The Earth's ionosphere embedded in the thermosphere is a coupled system influenced by solar and magnetospheric processes from above, as well as by upward propagating disturbances from below. This open session is suitable for contributions on all aspects of ionospheric physics. The session invites (multi)instrumental ground-based and satellite observations, simulations and modelling studies that address the dynamics of the ionosphere, concerning transient events, plasma waves and irregularities, as well as large-scale dynamics and long-term variations. Contributions dealing with magnetospheric forcing are sought in the areas of ionospheric phenomena caused by CME- and particularly by CIR/CH HSS-related magnetic storms and substorms. New results that focus on investigation of latitudinal, seasonal and hemispherical effects of the storms and substorms on ionosphere are especially appreciated. As for atmospheric forcing, contributions are sought that focus on atmospheric waves, wave-wave and wave-mean flow interactions, atmospheric electricity and electrodynamical coupling processes. New results on MLT feeding (wave penetration and secondary wave generation) of ionospheric disturbances and the solar effect on the vertical propagation conditions of the atmospheric waves are welcome.

Convener: Dalia Buresova | Co-convener: A. Belehaki
| Attendance Thu, 07 May, 08:30–12:30 (CEST)

Files for download

Download all presentations (226MB)

Chat time: Thursday, 7 May 2020, 08:30–10:15

Chairperson: Dalia Buresova
D2983 |
Glyn Collinson, Alex Glocer, Robert Pfaff, Robert Michell, Aroh Barjatya, James Clemmons, Frank Eparvier, Suzanne Imber, Mark Lester, David Mitchell, Max King, and Scott Bissett

Earth’s primary ionospheric loss process is the polar wind, which flows outwards along open magnetic field lines above our polar caps. One key component critical to the formation of this outflow is thought to be a weak ambipolar electric field. The potential drop resulting from this electric field is thought to assist terrestrial atmospheric escape since it reduces the potential barrier required for heavier ions (such as O+) to escape and accelerates light ions (such as H+) to escape velocity. Although a key component to atmospheric loss, Earth’s ambipolar electric field has never been measured due to its weak strength.


We announce the NASA Endurance mission, launching in 2022, which will attempt to make the first direct in-situ observations of Earth’s ambipolar electric field. Endurance launch from Ny-Ålesund, Svalbard, and soar across the exobase to altitudes greater than 800km. The spacecraft will be equipped with a new type of scientific instrument which will enable the Endurance to measure the total electric potential drop below her. She will also be equipped with a full array of sensors that will enable the science team to self-consistently model the polar wind during the flight to test our current theoretical understanding of the physical processes which generate Earth’s ambipolar electric field.

Endurance will perform groundbreaking discovery science, measuring a fundamental property of Earth for the first time: the strength of the ambipolar electric field generated by its ionosphere. The results will provide us with a better understanding of atmospheric escape at Earth, and why our planet is habitable.

How to cite: Collinson, G., Glocer, A., Pfaff, R., Michell, R., Barjatya, A., Clemmons, J., Eparvier, F., Imber, S., Lester, M., Mitchell, D., King, M., and Bissett, S.: “Endurance”, a new NASA mission to gauge Earth’s polar wind ambipolar electric field, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1968, https://doi.org/10.5194/egusphere-egu2020-1968, 2020.

D2984 |
James Wild, Daniel Billett, Keisuke Hosokawa, Adrian Grocott, Anasuya Aruliah, Yasunobu Ogawa, Satoshi Taguchi, and Mark Lester

Using data from the Scanning Doppler Imager, the Super Dual Auroral Radar Network, the EISCAT Svalbard Radar and an auroral all-sky imager, we examine an instance of F-region neutral winds which have been influenced by the presence of poleward moving auroral forms near the dayside cusp region. We observe a reduction in the time taken for the ion-drag force to re-orientate the neutrals into the direction of the convective plasma (on the order of minutes), compared to before the auroral activity began. Additionally, because the ionosphere near the cusp is influenced much more readily by changes in the solar wind via dayside reconnection, we observe the neutrals responding to an interplanetary magnetic field change within minutes of it occurring. This has implications on the rate that energy is deposited into the ionosphere via Joule heating, which we show to become dampened by the neutral winds.

How to cite: Wild, J., Billett, D., Hosokawa, K., Grocott, A., Aruliah, A., Ogawa, Y., Taguchi, S., and Lester, M.: Multi-instrument Observations of Ion-Neutral Coupling in the Dayside Cusp, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11789, https://doi.org/10.5194/egusphere-egu2020-11789, 2020.

D2985 |
Magnar G. Johnsen, Njål Gulbrandsen, Paul Hillman, Craig Denman, Jürgen Matzka, Volkmar Schultze, and Ulf-Peter Hoppe

In December 2019, for the first time, we were able to remotely measure the magnetic field in the mesospheric sodium layer, in the auroral zone.

By means of laser optical pumping and Larmor-resonance detection, it is possible to use the naturally occurring sodium layer in the mesosphere to measure Earth’s magnetic field magnitude at 90 km above ground. This is an altitude otherwise only accessible by rockets, which only will provide point measurements of very short time scales.

During the winter of 2019-20 we have applied a cw sum-frequency fasor/laser for probing the sodium-atom Larmor resonance at the Artic Lidar Observatory for Mesospheric Research (ALOMAR) at Andøya in northern Norway in order to measure and monitor the magnetic field in situ in the high latitude mesosphere over longer time scales.

The technique, which has been proved earlier at mid-latitudes, has now been confirmed and applied to high latitudes in the auroral zone during disturbed auroral and geomagnetic conditions. The magnetic field in the auroral zone is close to vertical making our measurements a notable achievement since the beam is closer to parallel with the magnetic field, contary to earlier measurements being closer to perpendicular as shown as best by theory.

This opens up for a completely new domain of measurements of externally generated geomagnetic variations related to currents in the magnetosphere-ionosphere system.

Here we report on the instrumental setup, and discuss our measurements of the mesospheric magnetic field.

How to cite: Johnsen, M. G., Gulbrandsen, N., Hillman, P., Denman, C., Matzka, J., Schultze, V., and Hoppe, U.-P.: First measurements of the Mesospheric Magnetic Field in the Auroral Zone by means of laser, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7839, https://doi.org/10.5194/egusphere-egu2020-7839, 2020.

D2986 |
Masatoshi Yamauchi, Magnar Johnsen, and Carl-Fredrik Enell

Solar flares are known to enhance the ionospheric electron density in the D- and E-region, enhancing twin vortex pattern in the dayside (e.g., Curto et al., 1994).  The geomagnetic deviation due to this current system is called as "crochet" or "SFE (solar flare effect)".  For X-flares, the crochet is easily detected as an enhancement in ASY-D index (Sing et al., 2012).  Since the effect is expected stronger at low solar zenith angles where solar radiation is high, high-latitude behavior (> 70° geographic latitudes: GGlat) has not been well studied and simply assumed as minor (such as weak return current).

However, the X flares on 6 September 2017 (X2.2 at 9 UT and X9.3 at 12 UT), caused large non-substorm geomagnetic disturbances at high latitudes, lasting much longer than the burst of electron density enhancement in the the D- and E-region (Yamauchi et al., 2018).  Both the polarity and duration turned out to be different from mid-latitude crochet which is characterized by short-lived (< 30 min) dH<0: dH is positive for over 5 hours with much higher amplitude than the crochet although the event took place near equator.  In addition, this dH showed oscillations on the order of 30 minute.  Since the X-ray intensity during 12-17 UT was higher than X-flare criterion until 17 UT, this long-lasting dH>0 with peak at 74-75 GGLat must also be caused by the X-flare.  The EISCAT radar data showed strong enhancement of convection lasting hours after the flare onset and relevant bursty (< 10 min) enhancement of the electron density.  This is consistent with long-lasting positive dH.  On the other hand, density oscillation period is about 15 min and different from the oscillation period of dH.   

Using Norwegian geomagnetic chain and EISCAT data, we examined X flares (> X2.0) for past two solar cycles, and found that (1) dH>0 at > 70 GGLAT with dH<0 (and positive ASY-D change is quite common) at lower latitude, (2) duration of crochet (dH<0) is shorter at higher latitude as the start timing and amplitude of dH>0 becomes earlier and larger at higher latitude, (3) at some latitude, crochet (dH<0) disappears and dH>0 dominates the entire period much longer than the crochet, and (4) electron density enhancement is spike-like no matter the duration of X-flare.  We interpret this long-lasting dH>0 is caused by independent mechanism from crochet.

Curto et al. (1994): doi:10.1029/93JA02270
Singh et al. (2012): doi:10.1016/j.jastp.2011.12.010
Yamauchi et al. (2018): doi:10.1029/2018SW00193

How to cite: Yamauchi, M., Johnsen, M., and Enell, C.-F.: Solar flare effect on the ionospheric current in the polar region: a new phenomena, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7934, https://doi.org/10.5194/egusphere-egu2020-7934, 2020.

D2987 |
| Highlight
Minna Palmroth, Maxime Grandin, Matti Helin, Pirjo Koski, Arto Oksanen, Minna Glad, Rami Valonen, Kari Saari, Emma Bruus, Johannes Norberg, Ari Viljanen, Kirsti Kauristie, and Pekka Verronen

Auroral forms are like fingerprints linking optical features to physical phenomena in the near-Earth space. While discovering new forms is rare, recently scientists reported of citizens' observations of STEVE, a pinkish optical manifestation of subauroral ionospheric drifts that were not thought to be visible to the naked eye. Here, we present a new auroral form named "the dunes". On Oct 7, 2018, citizen observers took multiple digital photographs of the same dunes simultaneously from different locations in Finland and Sweden. We develop a triangulation method to analyse the photographs, and conclude that the dunes are a monochromatic wave field with a wavelength of about 45 km within a thin layer at 100 km altitude. Supporting data suggest that the dunes manifest atmospheric waves, possibly mesospheric bores, which are rarely detected, and have not previously been observed via diffuse aurora, nor at auroral latitudes and altitudes. The dunes present a new opportunity to investigate the coupling of the lower/middle atmosphere to the thermosphere and ionosphere. We conclude that the the dunes may provide new insights into the structure of the mesopause as a response to driving by ionospheric energy deposition via Joule heating and electron precipitation. Further, our paper adds to the growing body of work that illustrates the value of citizen scientist images in carrying out quantitative analysis of optical phenomena, especially at small scales at subauroral latitudes. The dune project presents means to create general interest towards physics, emphasising that citizens can take part in scientific work by helping to uncover new phenomena.

How to cite: Palmroth, M., Grandin, M., Helin, M., Koski, P., Oksanen, A., Glad, M., Valonen, R., Saari, K., Bruus, E., Norberg, J., Viljanen, A., Kauristie, K., and Verronen, P.: Citizen scientists discover a new auroral form: Dunes provide insight into the upper atmosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2389, https://doi.org/10.5194/egusphere-egu2020-2389, 2020.

D2988 |
Amoré Nel and Mike Kosch

Black auroras are small-scale features that show a significant reduction in optical brightness, i.e. reduced flux of particle precipitation, compared to the surrounding diffuse aurora. It typically occurs post-substorm after magnetic midnight. This phenomenon also exhibits lower mean energy than the surrounding brighter aurora it is embedded in. The underlying mechanisms that cause black auroras are not yet fully understood, although several theories have been proposed: a coupled ionospheric-magnetospheric generation mechanism, and a magnetospheric generation mechanism. This shift in particle precipitation energy to a lower mean value is confirmed by using synchronised dual-wavelength optical and EISCAT incoherent scatter radar observations that ran in parallel, and agrees with the magnetospheric generation mechanism theory. Now reported for the first time is an even more elusive small-scale optical structure has been observed occurring paired with ~10% of black aurora patches. A patch or arc segment of enhanced luminosity, distinctly brighter than the diffuse background, which we name the anti-black aurora, may appear adjacent to the black aurora. The anti-black aurora always moves in parallel to the black aurora. The paired phenomenon always drifts with the same average speed in an easterly direction. From the first dual-wavelength observations of anti-black and black aurora pairs, we show that the anti-black and black auroras have a higher and lower mean energy, respectively, of the precipitating electrons compared to the diffuse background.

How to cite: Nel, A. and Kosch, M.: A new auroral phenomenon: The anti-black aurora, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5431, https://doi.org/10.5194/egusphere-egu2020-5431, 2020.

D2989 |
Hassanali Akbari and Robert Pfaff and the Auroral Jets Sounding Rocket Experiment Team

We present results from a 2017 sounding rocket experiment in which two NASA sounding rockets were simultaneously launched into the auroral ionosphere. The rockets included comprehensive instrumentation to measure DC and AC electric fields, magnetic fields, energetic particles, plasma density, and neutral winds, among other parameters, and achieved apogees of 190 and 330 km. This unprecedented collection of in-situ measurements obtained at two altitudes over an auroral arc, along with conjugate ground-based measurements by the Poker Flat incoherent scatter radar and all-sky cameras, enable us to investigate the behavior of an aurora arc and its associated electrodynamics. A prominent feature of our observations is the presence of localized, large-amplitude Alfvén wave structures observed in both the electric field and magnetometers at altitudes as low as 190 km in the vicinity of up- and down-ward current regions. The observations are discussed in the context of ionospheric feedback instability. The results are compared to predictions of previously published numerical studies and other sounding rocket observations.

How to cite: Akbari, H. and Pfaff, R. and the Auroral Jets Sounding Rocket Experiment Team: Auroral electrodynamics---investigation by a dual sounding rocket experiment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12853, https://doi.org/10.5194/egusphere-egu2020-12853, 2020.

D2990 |
Devin Huyghebaert, Adam Lozinsky, Glenn Hussey, Kathryn McWilliams, Draven Galeschuk, Jean-Pierre St. Maurice, Miguel Urco, Jorge Chau, and Juha Vierinen

The Ionospheric Continuous-wave E-region Bistatic Experimental Auroral Radar (ICEBEAR) is located in Canada and has a field of view centered at (58°N, 106°W) overlooking the terrestrial auroral zone.  This 49.5 MHz coherent scatter radar measures plasma density irregularities in the E-region ionosphere using a pseudo random noise phase modulated continuous-wave (CW) signal.  ICEBEAR uses this coded CW signal to obtain simultaneous high temporal (1 s) and spatial (1.5 km) resolutions of E-region plasma density turbulence over a 600 km x 600 km field of view, providing insights into the Farley-Buneman plasma density instability and wave-like structures evident in the coherent scatter.  The initial results from ICEBEAR were obtained with a 1D receiving array, providing azimuthal angle of arrival details of the incoming scattered signal.  This azimuthal determination, along with the range determined using the coded signal, allowed the scatter to be mapped in 2D.  A recent reconfiguration of the receiving array has allowed the elevation angle of the received signal to be calculated, providing 3D determination of the location of the plasma density irregularities.  This presentation will demonstrate the capabilities of ICEBEAR, displaying measurements of highly dynamic plasma density irregularities with wave-like behaviour on 1 second time scales.

How to cite: Huyghebaert, D., Lozinsky, A., Hussey, G., McWilliams, K., Galeschuk, D., St. Maurice, J.-P., Urco, M., Chau, J., and Vierinen, J.: ICEBEAR: Recent Results from a Bistatic Coded Continuous-Wave E-region Coherent Scatter Radar, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11558, https://doi.org/10.5194/egusphere-egu2020-11558, 2020.

D2991 |
| Highlight
Theodoros Sarris and the The Daedalus Science Study Team

The Daedalus mission has been proposed to the European Space Agency (ESA) in response to the call for ideas for the Earth Observation programme’s Earth Explorers. It was selected in 2018 as one of three candidates for Earth Explorer 10, and is currently undergoing a Phase-0 Science and Requirements Consolidation Study. The goal of the mission is to quantify the key electrodynamic processes that determine the structure and composition of the Lower Thermosphere-Ionosphere (LTI), focusing in particular on processes related to ion-neutral coupling. Daedalus will perform in-situ measurements of plasma density and temperature, ion drift, neutral density and wind, ion and neutral composition, electric and magnetic fields and precipitating particles. An innovative preliminary mission design allows Daedalus to perform these measurements down to altitudes of 140 km and below. These measurements will quantify the amount of energy locally deposited in the upper atmosphere via Joule heating and energetic particle precipitation, estimates of which currently vary by orders of magnitude between models. At the same time, the instrumentation of Daedalus will enable exploration of the variability and dynamics of the LTI, as well as science questions related to connections between the LTI and the atmosphere below. Daedalus will thus study the most under-explored region of the Earth's environment, the "agnostophere", which is the gateway between Earth’s atmosphere and space. In this presentation an overview of the Daedalus Mission Concept will be given, including the status of the ongoing Phase-0 Study.

How to cite: Sarris, T. and the The Daedalus Science Study Team: Daedalus: a Candidate ESA Earth Explorer Mission for the Exploration of the Lower Thermosphere-Ionosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20711, https://doi.org/10.5194/egusphere-egu2020-20711, 2020.

D2992 |
James M. Weygand, Paul Prikryl, Reza Ghoddousi-Fard, Lidia Nikitina, and Bharat S. R. Kunduri

High-speed streams (HSS) from coronal holes dominate solar wind structure in the absence of coronal mass ejections during solar minimum and the descending branch of solar cycle. Prominent and long-lasting coronal holes produce intense co-rotating interaction regions (CIR) on the leading edge of high-speed plasma streams that cause recurrent ionospheric disturbances and geomagnetic storms. Through solar wind coupling to the magnetosphere-ionosphere-atmosphere (MIA) system they affect the ionosphere and neutral atmosphere at high latitudes, and, at mid to low latitudes, by the transmission of the electric fields [1] and propagation of atmospheric gravity waves from the high-latitude lower thermosphere [2].

The high-latitude ionospheric structure, caused by precipitation of energetic particles, strong ionospheric currents and convection, results in changes of the GPS total electron content (TEC) and rapid variations of GPS signal amplitude and phase, called scintillation [3]. The GPS phase scintillation is observed in the ionospheric cusp, polar cap and auroral zone, and is particularly intense during geomagnetic storms, substorms and auroral breakups. Phase scintillation index is computed for a sampling rate of 50 Hz by specialized GPS scintillation receivers from the Canadian High Arctic Ionospheric Network (CHAIN). A proxy index of phase variation is obtained from dual frequency measurements of geodetic-quality GPS receivers sampling at 1 Hz, which include globally distributed receivers of the RT-IGS network that are monitored by the Canadian Geodetic Survey in near-real-time [4]. Temporal and spatial changes of TEC and phase variations following the arrivals of HSS/CIRs [5] are investigated in the context of ionospheric convection and equivalent ionospheric currents derived from  a ground magnetometer network using the spherical elementary current system method [6,7].

The Joule heating and Lorentz forcing in the high-latitude lower thermosphere have long been recognized as sources of internal atmospheric gravity waves (AGWs) [2] that propagate both upward and downward, thus providing vertical coupling between atmospheric layers. In the ionosphere, they are observed as traveling ionospheric disturbances (TIDs) using various techniques, e.g., de-trended GPS TEC maps [8].

In this paper we examine the influence on the Earth’s ionosphere and atmosphere of a long-lasting HSS/CIRs from recurrent coronal holes at the end of solar cycles 23 and 24. The solar wind MIA coupling, as represented by the coupling function [9], was strongly increased during the arrivals of these HSS/CIRs.


[1] Kikuchi, T. and K. K. Hashimoto, Geosci. Lett. , 3:4, 2016.

[2] Hocke, K. and K. Schlegel, Ann. Geophys., 14, 917–940, 1996.

[3] Prikryl, P., et al., J. Geophys. Res. Space Physics, 121, 10448–10465, 2016.

[4] Ghoddousi-Fard et al., Advances in Space Research, 52(8), 1397-1405, 2013.

[5] Prikryl et al. Earth, Planets and Space, 66:62, 2014.

[6] Amm O., and A. Viljanen, Earth Planets Space, 51, 431–440, 1999.

[7] Weygand J.M., et al., J. Geophys. Res., 116, A03305, 2011.

[8] Tsugawa T., et al., Geophys. Res. Lett., 34, L22101, 2007.

[9] Newell P. T., et al., J. Geophys. Res., 112, A01206, 2007.

How to cite: Weygand, J. M., Prikryl, P., Ghoddousi-Fard, R., Nikitina, L., and Kunduri, B. S. R.: Recurrent high-speed solar wind co-rotating interaction region imprint on the ionosphere and atmosphere: GPS TEC variations and atmospheric gravity waves, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6464, https://doi.org/10.5194/egusphere-egu2020-6464, 2020.

D2993 |
David Altadill, Antoni Segarra, Estefania Blanch, José Miguel Juan, Dalia Buresova, Ivan Galkin, Anna Belehaki, Haris Haralambous, and Claudia Borries

Traveling Ionospheric Disturbances (TIDs) are wave-like propagating irregularities that alter the electron density environment and play an important role spreading radio signals propagating through the ionosphere.

TechTIDE project, funded by the European Commission Horizon 2020 research and innovation program, is establishing a pre-operational system to issue warnings of the occurrence of TIDs over the region extended from Europe to South Africa based on the reliability of a set of TID detection methodologies.

This contribution aims at presenting the different methods and techniques of identification and tracking the activity of TIDs and their respective performance, that serve to feed the warning system of TechTIDE.

How to cite: Altadill, D., Segarra, A., Blanch, E., Juan, J. M., Buresova, D., Galkin, I., Belehaki, A., Haralambous, H., and Borries, C.: Identification and monitoring techniques of TIDs in the H2020 TechTIDE project , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7769, https://doi.org/10.5194/egusphere-egu2020-7769, 2020.

D2994 |
| solicited
Sergio Magdaleno and Joanna Rupiewicz

The European Geostationary Navigation Overlay Service (EGNOS) is the Europe's regional satellite-based augmentation system (SBAS). It provides an augmentation service to the Global Positioning System (GPS) L1 Coarse/ Acquisition (C/A) civilian signal by providing corrections and integrity information for GPS space vehicles (ephemeris, clock errors) and information to estimate the ionosphere delays affecting the user. This information provided by EGNOS improves the accuracy and reliability of GNSS positioning information while also providing a crucial integrity message. This is especially relevant for civil aviation community, which, thanks to this improvement, can perform precision approaches (APV-I and LPV200) using GNSS, with a clear optimisation of the cost of the infrastructure with no impact in the safety of the operations.

One of the most important figures for EGNOS is the availability of the system, which is characterized by the proportion of time during which reliable navigation information is presented to the crew, autopilot, or other system managing the flight of the aircraft. (ICAO SARPS).

ESSP, as EGNOS Service Provider, monitors the daily availability for these flight operations (APV-I, LPV200), considering the system available when operational requirements defined in ICAO SARPS are met. In this case, EGNOS is considered available when the Protection Levels, an upper bound of the aircraft position error with the specified integrity risk, are lower than the Alarm limits defined by ICAO for these operations.

One of the main degradation sources in the EGNOS availability (and others SBAS) is the ionosphere, especially under disturbance conditions (e.g. geomagnetic storms, scintillation …) (Pintor et al., 2015; Haddad, 2016).

In the frame of the H2020 project - TechTIDE, the impact of disturbed ionospheric conditions in the EGNOS availability has been analysed. TechTIDE project is generating a warning system which will provide Travelling Ionospheric Disturbances (TID) information and some ionospheric activity indicators. These products would be used for the definition of mitigation strategies in some operational systems (EGNOS, N-RTK and HF communications).

As part of TechTIDE project, ESSP has assessed the impact of disturbed ionospheric conditions in EGNOS availability and defined a relationship with an ionospheric activity indicator provided by TechTIDE warning system. This paper presents the outcomes of this assessment.


Haddad, F. (2016). Latest SBAS Performances under Severe and Equatorial Ionosphere Conditions, ICAO Workshop, August, 15-17, 2016.

Pintor, P., Roldan, R., Gomez, J., de la Casa, C., Fidalgo, R. M. (2015). The impact of the high ionospheric activity in the EGNOS performance, Coordinates, March 2015.

How to cite: Magdaleno, S. and Rupiewicz, J.: Impact of disturbed ionospheric conditions in EGNOS performance, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13966, https://doi.org/10.5194/egusphere-egu2020-13966, 2020.

D2995 |
Nicolas Bergeot, John Bosco Habarulema, Jean-Marie Chevalier, Tshimangadzo Matamba, Elisa Pinat, Pierre Cilliers, and Dalia Burešová

An increasing demand for a better modelling and understanding of the Ionosphere-Plasmasphere system (I/Ps) is required for both scientific and public practical applications using electromagnetic wave signals reflecting on or passing through this layer. This is the case for the Global Navigation Satellite Systems (GNSS, i.e. GPS, GLONASS, Galileo) and for spacecraft designers and operators who need to have a precise knowledge of the electron density distribution.

Additionally, despite the long-term ionospheric studies that have been on-going for many decades, a number of aspects are still complicated to understand and forecast accurately even in mid-latitude regions during quiet conditions. Performing inter-hemispherical climatological studies in European and South African regions should highlight differences/similarities in I/Ps response during different phases of solar activity and geophysical conditions.

In that frame, the Royal Observatory of Belgium (ROB) and the South African National Space Agency (SANSA) started a collaboration named “Interhemispheric Comparison of the Ionosphere-Plasmasphere System” (BEZA-COM). The goal is to provide inter-hemispheric comparison of the I/Ps implying: (1) a characterization of the climatological behavior of the Total Electron Content (TEC) in the I/Ps, over European, South African, Arctic and Antarctica regions; (2) an identification of the mechanisms that regulate inter-hemispheric differences, asymmetries and commonalities in the I/Ps from low to high-latitudes, (3) study of the different responses of the I/Ps during extreme solar events and induced geomagnetic storms in the two hemispheres.

In this paper, we reprocessed the GNSS data (GPS+GLONASS) of the dense EUREF Permanent GNSS Network (EPN) and South African TRIGNET networks as well as IGS stations for the period 1998-2018. The output consists in vertical Total Electron Content (vTEC), estimated every 15 min., and covering the central European and South African regions. The vTEC is then extracted at two conjugated locations and used to constrain empirical models to highlight the climatological behavior of the ionospheric vTEC over Europe and South Africa. From the results, we will show that the differences are quite significant. To give first answers on these differences, we also compared these models with ionosondes long-term data based models (for foF2 and hmF2) at two conjugated locations (Grahamstown and Průhonice) as well as long-term NRLMSISE O/N2 ratio.

How to cite: Bergeot, N., Habarulema, J. B., Chevalier, J.-M., Matamba, T., Pinat, E., Cilliers, P., and Burešová, D.: Inter-hemispheric comparison of the ionosphere-plasmasphere system from multi-instrumental/model approach. , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18657, https://doi.org/10.5194/egusphere-egu2020-18657, 2020.

D2996 |
Artem Vesnin, Yury Yasyukevich, Boris Maletckii, Alexander Kiselev, Ilya Zhivetiev, Ilya Edemskiy, and Semen Syrovatskiy

System for the Ionosphere Monitoring and Researching from GNSS (SIMuRG, see https://simurg.iszf.irk.ru) has been developed in ISTP SB RAS. The system servers as proxy for the RINEX data of global GNSS receivers network. SIMuRG automatically downloads, process and visualize GNSS data. Despite of the system takes routine processing task from the researches, which is valuable by itself, it provides newly developed and improved data products. All data products are based on total electron content (TEC) calculated from RINEX and global ionospheric maps GIM. The first data product is ionospheric variations (TEC variations). The variations are widely used for ionospheric studies, but SIMuRG performs calculation using the filtration that suits TEC data the best way. Before new filtration technique was applied major unphysical artifacts were detected in the data. The artifacts could even prevent from correct interpretation of processing results. The variations together with widely used ROTI index which is also implemented in the system helps to study ionospheric variability. The second data product is newly developed “adjusted TEC”. For that we use GIM to force all TEC series from different site-satellite line-of-sights have one reference level. While the reference level is the same, adjusted TEC leaves all the peculiarities exhibited in different TEC series unaffected. Adjusted TEC broaden ionospheric maps capability near the GNSS stations improving time resolution up to 30 seconds and giving better space resolution. The third data product is implementation of D1 method which calculates ionospheric irregularities motion velocity. D1 shows velocity vector while variations show only amplitude of the irregularity (deviation from the background). D1 calculation is designed in the way that it possible to choose scale of the disturbance to study. It makes possible to study the disturbances of different physical origin. D1 is able to show global ionospheric dynamics and can help detect traveling ionospheric disturbances of various scales. The data described above are attribute by the interactive experimental geometry plots, which might consider as one more data product. The geometry plots might be useful since the TEC data cover area of several thousands kilometers across. The fourth data product is global and regional electron content (GEC and REC), see https://simurg.iszf.irk.ru/gec for reference. SIMuRG provides interactive plots of the GEC and REC. While TEC shows the number of electrons in a given direction (surface density), GEC and REC show amount of a plasma in a volume. GEC is weighted sum of the TEC around the globe, REC – in some geographical region. GEC and REC suits for large scale long-living ionospheric variations studies. Using REC we detect after-storm plasma density change in equatorial ionosphere. There is an option to choose region for REC using geographic and geomagnetic coordinates. We also developed the interface for ionospheric events tracking and submission. We hope to use the events database for machine learning purpose. We hope all above newly developed and improved TEC based data products find application among researches.

This work was performed under the Russian Science Foundation Grant No. 17-77-20005.

How to cite: Vesnin, A., Yasyukevich, Y., Maletckii, B., Kiselev, A., Zhivetiev, I., Edemskiy, I., and Syrovatskiy, S.: Total electron content driven data products of SIMuRG, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21635, https://doi.org/10.5194/egusphere-egu2020-21635, 2020.

D2997 |
Dalia Buresova, John Bosco Habarulema, Jurgen Watermann, Ilya K. Edemskiy, Jaroslav Urbar, David Altadill, Estefania Blanch, Antoni Segara, and Zama Katamzi

The paper presents results of the analysis of the changes in the regular ionospheric variability and TID activity observed during CIR/HSSS-related storms. We analyzed main ionospheric parameters retrieved from manually scaled ionograms, plasma drift measurements and TEC data obtained from several European and African ionospheric stations and GNSS receivers. Most of the observed storm-related TIDs had periods of 60-180 min (LSTIDs). During the analyzed storms we also observed extraordinary spreads and plasma bubbles at the F region heights. The results of the analysis were compared with the TID activity during strong magnetic storms of CME origin along the European-African sector. In order to obtain quantitative information on the likeliness and morphology of interhemispheric circulation of LSTIDs at about 40 events were examined lasting between 8 and 24 hours each. We used exclusively GPS-based detection methods, specifically information on TEC, TEC deviations in space and time from a background reference (dTEC), and the Rate of TEC change in time (ROT), all inferred from GPS receiver networks in Europe and Africa. We conclude that hemispheric conjugacy of LSTID is highly probable while interhemispheric circulation rather unlikely but still occurring during some periods.

How to cite: Buresova, D., Habarulema, J. B., Watermann, J., Edemskiy, I. K., Urbar, J., Altadill, D., Blanch, E., Segara, A., and Katamzi, Z.: CIR/HSSS-related TID activity and their interhemispheric circulation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7016, https://doi.org/10.5194/egusphere-egu2020-7016, 2020.

D2998 |
Yang-Yi Sun, Chieh-Hong Chen, Jann-Yenq Liu, and Tsung-Yu Wu

Solar activities can disturb the ionosphere globally and induce ionospheric weather phenomena that transit rapidly through a large area. By contrast, sometimes the ionospheric plasma density can remain high or low over a certain location for a few days, which are difficult to be attributed to solar activities. This study shows the location preference of the positive and negative total electron content (TEC) anomalies persisting continuously longer than 24 hours (cross the two terminators) at middle and low latitudes (within ±60ºN geomagnetic latitudes). The TEC is obtained from the global ionospheric map (GIM) of the Center for Orbit Determination in Europe (CODE) (ftp://cddis.gsfc.nasa.gov/pub/gps/products/ionex) under the geomagnetic quiet condition of Kp ≤ 3o during the period of 2005–2018. There are a few (less than 4%) TEC anomalies that can persist over 24 hours. The persistence of the positive TEC anomaly along the ring of fire on the western edge of the Pacific Ocean. The high persistence of the TEC anomalies at midlatitudes suggests that thermospheric neutral wind contributes to the anomaly formation. The temporal and spatial anomalies of the ionospheric electric field, atmospheric electric field (flash), atmospheric gravity wave, and neutral wind over the ring of fire should be further examined for explaining whether the persistence of the TEC anomalies associates with lithospheric activities.

How to cite: Sun, Y.-Y., Chen, C.-H., Liu, J.-Y., and Wu, T.-Y.: Global distribution of persistence of total electron content anomaly, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9389, https://doi.org/10.5194/egusphere-egu2020-9389, 2020.

D2999 |
Attila Buzas, Veronika Barta, and Daniel Kouba

The most intense external force affecting the ionosphere from above is related to large solar flare events, therefore it is of particular importance to study their impact on the ionosphere. During solar flares, the suddenly increased radiation causes increased ionization and enhanced absorption of radio waves leading to partial or even total radio fade-out lasting for hours in some cases (e. g. [1] [2]).


The ionospheric response to large solar flares have been investigated using the ionosonde data measured at Pruhonice (PQ052, 50°, 14.5°) in September 2017, the most active solar period of Solar Cycle 24. A novel method [3] to calculate and investigate the absorption of radio waves propagating in the ionosphere is used to determine the absorption during large solar flare events (M and X class). Subsequently, the absorption data are compared with the indicators derived from the fmin method (fmin, the minimum frequency is considered as a qualitative proxy for the “nondeviative” radio wave absorption occurring in the D-layer). Total and partial radio fade-out and increased values (with 2-5 MHz) of the fmin parameter were experienced during and after the intense solar flares (> M3). The combination of these two methods may prove to be an efficient approach to monitor the ionospheric response to solar flares.


[1] Sripathi, S., Balachandran, N., Veenadhari, B., Singh, R., and Emperumal, K.: Response of the equatorial and low-latitude ionosphere to an intense X-class solar flare (X7/2B) as observed on 09 August 2011, J. Geophys. Res.-Space, 118, 2648–2659, 2013.

[2] Barta, V., Sátori, G., Berényi, K. A., Kis, Á., and Williams, E. (2019). Effects of solar flares on the ionosphere as shown by the dynamics of ionograms recorded in Europe and South Africa. Annales Geophysicae, Vol. 37, No. 4, pp. 747-761

[3] Sales, G. S., 2009, HF absorption measurements using routine digisonde data, Conference material, XII. International Digisonde Forum, University of Massachusetts

How to cite: Buzas, A., Barta, V., and Kouba, D.: Studying the ionospheric absorption during large solar flare events in September 2017, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2924, https://doi.org/10.5194/egusphere-egu2020-2924, 2020.

D3000 |
Yi-Wun Chen and Chi-Kuang Chao

  A remote sensing satellite, FORMOSAT-5, developed by National Space Organization (NSPO) carried a piggyback science payload, Advanced Ionospheric Payload (AIP), for space weather and seismo-ionospheric precursor study.  To meet the science requirements, AIP could be operated in different measurement modes to obtain various plasma parameters.  The first AIP measurement was performed on 7 September 2017 to obtain the first-orbit data and started routine operation in November the same year.  Global ion density and ion velocity/temperature distributions were available every two days and four days, respectively.  AIP was regularly operated in a sampling rate 1,024 Hz to maximize useful science data.  In this poster, global occurrence rates of pre-midnight low-latitude ionospheric plasma density irregularities will be shown from AIP science data collected since winter 2017.  The results indicate that seasonal variations of the occurrence rates during the solar minimum (2017/11-2019/12) are distributed very similar to but have lower magnitudes than those observations by ROCSAT-1/Ionospheric Plasma and Electrodynamics Instrument dataset (1999-2004) during solar maximum.

How to cite: Chen, Y.-W. and Chao, C.-K.: Global Occurrence Rates of Ionospheric Plasma Density Irregularities Observed by Advanced Ionospheric Probe Onboard FORMOSAT-5 Satellite During Solar Minimum, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3210, https://doi.org/10.5194/egusphere-egu2020-3210, 2020.

D3001 |
Michael Danielides and Jaroslav Chum

Earth's ionosphere is formed mainly due to solar radiation, precipitating particles and cosmic rays. Its behavior is directly dependent on solar variation and the change of solar activity through out each solar cycle. The solar activity is measured by the number of sunspots and the solar radiation flux expressed by the F10.7 index. The earlier variation in electron density from solar cycle maximum to solar cycle minimum has been noted by Hargreaves (1992). He utilized the F10.7 index as a proxy for Lyman- radiation flux, which ionizes at D-region heights mainly O2 and N2 also NO. Utilizing the IRI model the atmospheric densities of O2 and N2 are assumed to be constant, NO density is the unknown. Also, it is known that the ionospheric reflection height depends on, e.g. diurnal variations [Pal & Chakrabarti, 2010] and other sudden ionospheric disturbances. Its longer term variations are not well enough studied.

Utilizing passive VLF ground based measurements with data coverage for almost the entire solar cycle 24, we compare monthly averaged solar quiet absorption curves fitted by a cosine dependence. This cosine dependence includes fixed parameters based on geography and setup of the instrument. The variables are only the solar zenith angle and the D-region absorption. This approach offers an indirect value of NO density change.

For the present study we utilize VLF monitors, which are located in northern Germany and at Czech Republic. The latter station also offers data from ionospheric sounder and continuous Doppler sounding. A simple 1-D ionospheric model is applied to compute ionospheric electron densities for daytime conditions based on solar F10.7 radiation fluxes.

The aim of this study is a comparison of solar quiet VLF curves of the solar cycle 24 maximum and minimum. Beside the change of NO density, also the variation of height of the D-region reflective layer will be discussed.

How to cite: Danielides, M. and Chum, J.: Comparison of D-Region Absorption During Solar Cycle 24, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3368, https://doi.org/10.5194/egusphere-egu2020-3368, 2020.

D3002 |
Josephine Salice, Hilde Nesse Tyssøy, Christine Smith-Johansen, and Eldho Midhun Babu

Energetic electron precipitation (EEP) into the Earth’s atmosphere can collide with gases and deposit their energy there. The collisions between electrons and atmospheric gasses initiate several chemical reactions which can reduce the ozone concentration. Ozone is critically important in the middle atmosphere energy budget as changes in the ozone concentration impact temperature and winds. EEP is not fully understood in terms of how much energy is being deposited and what the associated drivers are.  An accurate quantification of EEP has limitations due to instrumental challenges and therefore imposes limitations of the associated EEP parameterization into climate models. A solution to this problem is a better understanding of the driver processes of energetic electron acceleration and precipitation, alongside optimized measurements. In this study the bounce loss cone fluxes are inferred from EEP measurements by MEPED on board NOAA/POES and EUMETSAT/METOP at tens of keV to relativistic energies. It investigates EEP in contexts of three different solar wind structures: high-speed streams, coronal mass ejections, and ambient or slow interstream solar wind, as well as geomagnetic activity. The study will focus on the year 2010 and aim to understand the context EEP is created in, which will allow a more accurate estimate of the EEP to be applied in atmospheric climate models

How to cite: Salice, J., Tyssøy, H. N., Smith-Johansen, C., and Babu, E. M.: The link between solar wind structures, geomagnetic indices, and energetic electron precipitation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4956, https://doi.org/10.5194/egusphere-egu2020-4956, 2020.

D3003 |
Chi-Kuang Chao

A FORMOSAT-5 satellite has been launched on 25 August 2017 CST into a 98.28° inclination sun-synchronous circular orbit at 720 km altitude along the 1030/2230 local time sectors.  The orbital coverage provides a great opportunity to survey terrestrial ionosphere from equatorial to polar region every two days.  Advanced Ionospheric Probe (AIP) is a piggyback science payload developed by National Central University for the FORMOSAT-5 satellite to measure ionospheric plasma concentrations, velocities, and temperatures.  It is also capable of measuring ionospheric plasma density irregularities at a sample rate up to 8,192 Hz over a wide range of spatial scales.  In this poster, global ion density distributions observed by FORMOSAT-5/AIP in the pre-midnight sector can be averaged monthly and seasonally from in-situ measurement since November 2017.  Wave-3 and wave-4 patterns are clearly detected from the distributions and varied with season and solar cycle.  It is adversely indicated that FORMOSAT-5/AIP can provide high quality data to identify long-term ionospheric ion density variations.

How to cite: Chao, C.-K.: Global Ion Density Distributions Observed by Advanced Ionospheric Probe Onboard FORMOSAT-5 Satellite, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6421, https://doi.org/10.5194/egusphere-egu2020-6421, 2020.

D3004 |
Eldho Midhun Babu, Hilde Nesse Tyssøy, Christine Smith-Johnsen, Ville Aleksi Maliniemi, Josephine Alessandra Salice, and Robyn Millan

Energetic electron precipitation (EEP) from the plasma sheet and the radiation belts, can collide with gases in the atmosphere and deposit their energy. EEP increase the production of NOx and HOx, which will catalytically destroy stratospheric ozone, an important element of atmospheric dynamics. The particle precipitation also causes variation in the radiation belt population. Therefore, measurement of latitudinal extend of the precipitation boundaries is important in quantifying atmospheric effects of Sun-Earth interaction and threats to spacecrafts and astronauts in the Earth’s radiation belt.
This study uses measurements by MEPED detectors of six NOAA/POES and EUMETSAT/METOP satellites during the year 2010 to determine the latitudinal boundaries of EEP and its variability with geomagnetic activity and solar wind drivers. Variation of the boundaries with respect to different particle energies and magnetic local time is studied. The result will be a key element for constructing a model of EEP variability to be applied in atmosphere climate models.

How to cite: Babu, E. M., Tyssøy, H. N., Smith-Johnsen, C., Maliniemi, V. A., Salice, J. A., and Millan, R.: Determining latitudinal extent of energetic electron precipitation using MEPED on-board NOAA POES, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4963, https://doi.org/10.5194/egusphere-egu2020-4963, 2020.

D3005 |
Yiding Chen, Libo Liu, Huijun Le, and Hui Zhang

Interhemispheric coupling between the northern and southern mid-lattitude ionosphere through the plasmasphere is difficult to confirm directly from observations. A possible result induced by this coupling is interhemispheric conjugacy of the mid-latitude ionosphere. In this paper, interhemispheric conjugate effect in longitude variations of mid-latitude total ion density (Ni) is presented, for the first time, using the Defense Meteorological Satellite Program (DMSP) measurements; northern and southern Ni longitude variations at 21:30 LT are similar between magnetically conjugate mid-latitudes around solar minimum June Solstice of 1996. The conjugate effect after sunset also occurs around the June Solstice in other solar minimum years but disappears when solar activity increases. We suggested that mid-latitude interhemispheric coupling is responsible for the conjugate effect. Neutral wind induced ionospheric transport causes topside longitude variations via upward diffusion at summer mid-latitudes; this further induces similar longitude variations of topside Ni at winter mid-latitudes via the summer to winter interhemispheric coupling. The conjugate effect occurs only inside the plasmapause where magnetic flux tubes are closed and the plasma in these tubes can stably corotate with the Earth. The conjugate effect not only proves mid-latitude interhemispheric coupling through the plasmasphere, but also implies that neutral wind induced transport can affect ionospheric coupling to the plasmasphere at mid-latitudes.

How to cite: Chen, Y., Liu, L., Le, H., and Zhang, H.: Interhemispheric conjugate effect in longitude variations of mid-latitude ion density, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12549, https://doi.org/10.5194/egusphere-egu2020-12549, 2020.

Chat time: Thursday, 7 May 2020, 10:45–12:30

Chairperson: Dalia Buresova
D3006 |
Habtamu Tesfaw, Ilkka Virtanen, Anita Aikio, Lassi Roininen, and Sari Lasanen

Electron precipitation and ion frictional heating events cause rapid variations in electron temperature, ion temperature and F1 region ion composition of the high-latitude ionosphere. Four plasma parameters: electron density, electron temperature, ion temperature, and plasma bulk velocity, are typically fitted to incoherent scatter radar (ISR) data.

Many ISR data analysis tools extract the plasma parameters using an ion composition profile from an empirical model. The modeled ion composition profile may cause bias in the estimated ion and electron temperature profiles in the F1 region, where both atomic and molecular ions exist with a temporally varying proportion.

In addition, plasma parameter estimation from ISR measurements requires integrating the scattered signal typically for tens of seconds. As a result, the standard ISR observations have not been able to follow the rapid variations in plasma parameters caused by small scale auroral activity.

In this project, we implemented Bayesian filtering technique to the EISCAT’s standard ISR data analysis package, GUISDAP. The technique allows us to control plasma parameter gradients in altitude and time.

The Bayesian filtering implementation enabled us to fit electron density, ion and electron temperatures, ion velocity and ion composition to ISR data with high time resolution. The fitted ion composition removes observed artifacts in ion and electron temperature estimates and the plasma parameters are calculated with 5 s time resolution which was previously unattainable.

Energy spectra of precipitating electrons can be calculated from electron density and electron temperature profiles observed with ISR. We used the unbiased high time-resolved electron density and temperature estimates to improve the accuracy of the estimated energy spectra. The result shows a significant difference compared to previously published results, which were based on the raw electron density (backscattered power) and electron temperature estimates calculated with coarser time resolution.


How to cite: Tesfaw, H., Virtanen, I., Aikio, A., Roininen, L., and Lasanen, S.: Bayesian filtering for incoherent scatter radar analysis , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13374, https://doi.org/10.5194/egusphere-egu2020-13374, 2020.

D3007 |
Stephan C. Buchert

A so far simplified model considers the response of the magnetized ionosphere
to neutral winds and the so created effective electrodynamic coupling in
neutral atmosphere dynamics.  The effect resembels viscosity, but the
geomagnetic field couples winds also over large distances.  As a prominent
example the Sq variations are presented as a system that couples the winds
between hemispheres at magnetically conjugate points. The interaction between
hemispheres tends to force the large scale wind systems towards alignment with
magnetic coordinates and towards mirror symmetry with respect to the magnetic
equator. This is, however, for the Earth's thermosphere, never completed
because the time constant exceeds the 24 hours over which dynamics driven by
the energy input from solar radiation creates new winds.

Wind differences are so reduced and kinetic energy gets dissipated. From
observed magnetic Sq variations we estimate that a typical average dissipation
rate by interhemisphere electrodynamic coupling is roughly 0.1 to 1 % of the
heating rate resulting from the absorption of EUV solar radiation.

The same model applies when a neutral wind varies along the geomagnetic field
within the dynamo layer of the ionosphere, for example due to tides and gravity
waves. As a result such neutral wind variations also tend to get evened out and
Joule heat is produced. At mid and high latitudes so upward propagating gravity
waves get damped when they reach to ionospheric dynamo region.

How to cite: Buchert, S. C.: Electrodynamic Coupling and Dissipation of Thermospheric Winds, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16800, https://doi.org/10.5194/egusphere-egu2020-16800, 2020.

D3008 |
Nada Ellahouny, Anita Aikio, Marcus Pedersen, Heikki Vanhamäki, Ilkka Virtanen, Johannes Norberg, Maxime Grandin, Alexander Kozlovsky, Tero Raita, Kirsti Kauristie, Aurélie Marchaudon, Pierre-Louis Blelly, and Shin-ichiro Oyama

 Solar wind High-Speed Streams (HSSs) affect the auroral ionosphere in many ways, and several separate studies have been conducted of the different effects seen e.g. on aurora, geomagnetic disturbances, F-region behavior, and energetic particle precipitation. In this work, we study an HSS event in the solar cycle (24), which was associated with a co-rotating interaction region (CIR) that hit the Earth’s magnetopause at about 17:20 UT on 14 March 2016. The associated magnetic storm lasted for seven days, and the Dst index reached -56 nT. We use a very comprehensive set of measurements to study the whole period of this storm, following day by day for the magnetic indices and solar wind parameters and relating its consequences on ionospheric plasma parameters. We use EISCAT radar data from Tromsø and Svalbard stations to see the response in plasma parameters at different altitudes, riometer data for cosmic noise absorption, and IMAGE magnetometers to see the intensities of auroral electrojets. TomoScand ionospheric tomography provides us with electron densities over a wide region in Scandinavia and AMPERE data the global field-aligned currents. We identified 13 local substorms in the Scandinavian sector from the IL (IMAGE lower) index. Altogether, there were 11 global substorms, for which the AE index reaches 1000 nT. We discuss the development of currents, as well as E and D region precipitation during the course of this long-duration storm and compare local versus global behavior.

How to cite: Ellahouny, N., Aikio, A., Pedersen, M., Vanhamäki, H., Virtanen, I., Norberg, J., Grandin, M., Kozlovsky, A., Raita, T., Kauristie, K., Marchaudon, A., Blelly, P.-L., and Oyama, S.: Characteristics of a HSS-driven magnetic storm in the high-latitude ionosphere; A case study of 14th of March 2016 storm, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20550, https://doi.org/10.5194/egusphere-egu2020-20550, 2020.

D3009 |
Esa Kallio, Ari-Matti Harri, Anita Aikio, Arno Alho, Mathias Fontell, Riku Jarvinen, Kirsti Kauristie, Antti Kero, Antti Kestilä, Petri Koskimaa, Juha-Matti Lukkari, Olli Knuuttila, Jauaries Loyala, Joonas Niittyniemi, Johannes Norberg, Jouni Rynö, Esa Turunen, and Heikki Vanhamäki

The Suomi100 nanosatellite was launched on Dec. 3, 2018 (http://www.suomi100satelliitti.fi/eng). The 1 Unit (10 cm x 10 cm x 10 cm) polar orbit cubesat will perform geospace, ionosphere and arctic region research with a white light camera and a radio wave spectrometer instrument which operates in the 1-10 MHz frequency range.

Suomi 100 satellite type of nanosatellite, so called CubeSat, provides a cost effective possibility to provide in-situ measurements in the ionosphere. Especially, combined CubeSat observations with ground-based observations give a new view on auroras and associated electromagnetic phenomena. Especially joint CubeSat – ground based observation campaigns enable the possibility of studying the 3D structure of the ionosphere.

Increasing computation capacity has made it possible to perform simulations where properties of the ionosphere, such as propagation of the electromagnetic waves in the medium frequency, MF (0.3-3 MHz) and high frequency, HF (3-30 MHz), ranges is based on a 3D ionosphere model and on first-principles modelling. Electromagnetic waves at those frequencies are strongly affected by ionospheric electrons and, consequently, those frequencies can be used for studying the plasma. On the other hand, even if the ionosphere originally enables long-range telecommunication at MF and HF frequencies, the frequent occurrence of spatio-temporal variations in the ionosphere disturbs communication channels, especially at high latitudes. Therefore, study of the MF and HF waves in the ionosphere has both a strong science and technology interests.

We present computational simulation and measuring principles and techniques to investigate the arctic ionosphere by a polar orbiting CubeSat which radio instrument measures HF and MF waves. We introduce 3D simulations, which have been developed to study the propagation of the radio waves, both ground generated man-made radio waves and space formed space weather related waves, through the 3D arctic ionosphere with a 3D ray tracing simulation. We also introduce the Suomi100 CubeSat mission and its observations.

How to cite: Kallio, E., Harri, A.-M., Aikio, A., Alho, A., Fontell, M., Jarvinen, R., Kauristie, K., Kero, A., Kestilä, A., Koskimaa, P., Lukkari, J.-M., Knuuttila, O., Loyala, J., Niittyniemi, J., Norberg, J., Rynö, J., Turunen, E., and Vanhamäki, H.: Ionosphere research with a nanosatellite’s radio wave spectrometer, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13921, https://doi.org/10.5194/egusphere-egu2020-13921, 2020.

D3010 |
Elizabeth Donegan-Lawley, Alan Wood, Gareth Dorrian, Alexandra Fogg, Timothy Yeoman, and Sean Elvidge

Flow channel events have previously been observed breaking up polar cap patches on the dayside ionosphere but, to the best of our knowledge, have not been observed on the nightside. We report observations of a flow channel event in the evening of the 9th January 2019 under quiet geomagnetic conditions. This multi-instrument study was undertaken using a combination of multiple EISCAT (European Incoherent Scatter) radars, SuperDARN (Super Dual Auroral Radar Network), MSP (Meridian Scanning Photometer) and GNSS (Global Navigation Satellite System) scintillation data. These data were used to build a picture of the evening’s observations from 1800 to 2359 UT. The flow channel event lasted a total of 13 minutes and was responsible for segmenting a polar cap patch. A decrease in electron density was observed, from a patch value of 1.4x1011 m3 to a minimum value of 5x1010 m3. In addition, ion velocities in excess of 1000 ms-1 and ion temperatures of greater than 2000 K were also observed. 

How to cite: Donegan-Lawley, E., Wood, A., Dorrian, G., Fogg, A., Yeoman, T., and Elvidge, S.: Break up of a polar cap patch in the nightside ionosphere due to a flow channel event, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17726, https://doi.org/10.5194/egusphere-egu2020-17726, 2020.

D3011 |
Marcus Pedersen, Heikki Vanhamäki, Anita Aikio, Sebastian Käki, Ari Viljanen, Abiyot Workayehu, Colin Waters, and Jesper Gjerloev

High speed streams (HSS) and associated co-rotating interaction regions (CIR) in the solar wind are one of the major drivers of geomagnetic activity, especially during declining phases of sunspot cycles and near sunspot minima. We have identified 51 HSS/CIR driven geomagnetic storms that coincide with a Dst drop to less than -50nT during the period 2009-2018 and we investigate their impact on ionospheric current systems. Our approach is to study the evolution of the global scale current systems, i.e. the auroral electrojets and Region-1/2 field-aligned currents (FAC), with the SuperMAG magnetometers and AMPERE satellite data, respectively. The events are studied with a superposed epoch analysis centered at the storm onset to see the general behavior of the current system globally and in four different MLT sectors: noon, dusk, midnight and dawn. A minor enhancement of the integrated FAC was observed in the midnight, dawn and dusk sector 3 hours before the storm onset. The largest FAC and variability was observed in the dusk sector, and the integrated FAC maximum occurred in the middle of the storm main phase, 4 hours before the Dst minimum. This result will be compared to the evolution and behavior of the electrojet currents from superMAG. In the future a similar study will be conducted for ICME geomagnetic storms and compared to the HSS/CIR-related storms.

How to cite: Pedersen, M., Vanhamäki, H., Aikio, A., Käki, S., Viljanen, A., Workayehu, A., Waters, C., and Gjerloev, J.: Impact of Solar Wind High Speed Streams on Ionospheric Current Systems , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18592, https://doi.org/10.5194/egusphere-egu2020-18592, 2020.

D3012 |
Jan Laštovička

The relationship between ionospheric parameters and solar activity proxies has broadly been assumed to be stable. However, using data of foF2 from three European stations and foE from two European stations we show that this assumption is not correct. In more recent years the dependence of ionospheric parameters on solar proxies is steeper than in the past. The change is between 1994 and 1997 for foF2 and after 2000 for foE. Also the relationships among solar proxies have changed, which might indicate some solar changes perhaps responsible for the observed changes of the relationship between ionospheric parameters and solar proxies with implications to trend and climatological studies, and modeling.


How to cite: Laštovička, J.: The relationship between ionospheric parameters and solar proxies is changing – when?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3329, https://doi.org/10.5194/egusphere-egu2020-3329, 2020.

D3013 |
Ilya Edemskiy and Ilya Edemskiy

Localized enhancements of total electron content (TEC) are usually registered during magnetic storms and are often believed to be connected with storm enhanced density (SED) events. Investigating global ionospheric maps we found that such localized TEC enhancements (LTE) could be observed in Southern Hemisphere during both disturbed and quiet time with no clear dependence on parameters of near space. Analysis of occurrence of LTEs in the regions of Indian and Southern Atlantic Oceans showed that part of them (observed during magnetic storms and localized in subpolar latitudes) can be connected with SEDs. Since another part of subpolar LTEs is detected during relatively quiet conditions its generation mechanism should be different despite they have similar spatial distribution. Most of the enhancements are observed in middle latitudes and is detected during all the investigated years. The occurrence rate of LTEs hardly depends on solar activity and the most probable season for LTE detection is April-September (autumn-winter).

Here we investigate reasons of generation both midlatitudinal and subpolar LTEs trying to define the mechanisms of their generation in details.

How to cite: Edemskiy, I. and Edemskiy, I.: Localized enhancements of total electron content in Southern Hemisphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5300, https://doi.org/10.5194/egusphere-egu2020-5300, 2020.

D3014 |
John Bosco Habarulema, Nicolas Bergeot, Jean-Marie Chevalier, Elisa Pinat, Dalia Buresova, Tshimangadzo Matamba, and Zama Katamzi-Joseph

The ionospheric electron density response to the occurrence of geomagnetic storms remains one of the challenges that is less understood partially on both short and long-term scales. This is even more complicated given that different locations within the same latitude region (for example in mid-latitudes) at times show different electron density responses as a result of complex dynamic and electrodynamics processes that may be present during one storm duration.  Mid-latitude regions are influenced by storm induced processes originating from both low and high latitudes. Using a combination of ionosonde and Global Navigational Satellite Systems (GNSS) observations, we show differences and or similarities in the electron density response during selected storm periods in both northern and southern hemisphere over the Europe-African sector. Physical mechanisms at play within different storm phases are explored using both observations and empirical modeling efforts.  

How to cite: Habarulema, J. B., Bergeot, N., Chevalier, J.-M., Pinat, E., Buresova, D., Matamba, T., and Katamzi-Joseph, Z.: Interhemispheric comparison of the ionospheric electron density response during geomagnetic storm conditions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8268, https://doi.org/10.5194/egusphere-egu2020-8268, 2020.

D3015 |
Estefania Blanch, Antoni Segarra, David Altadill, Vadym Paznukhov, and Jose Miguel Juan

Travelling Ionospheric Disturbances (TIDs) are ionospheric irregularities that occur as plasma density fluctuations that propagate as waves through the ionosphere over a wide range of velocities and frequencies. It has been demonstrated that Large Scale TIDs (LSTID) can be detected with several ionospheric sensors such as ionosondes and their main characteristics such as velocity, direction of propagation and amplitude can be inferred.

We have applied the recent developed HF Interferometry (HF-Int) method to detect the occurrence and main characteristics of LSTIDs over Europe for different solar activities (2014 – 2019) in order to perform a climatological analysis. HF-Int determines the dominant period of oscillation and the amplitude of the LSTIDs using spectral analysis, and estimates the propagation parameters of the LSTIDs from the measured time delays of the disturbance detected at different sensor sites.

The results show that larger diurnal and seasonal occurrence of LSTID happens near sunrise hours and night-time, especially during equinox. In the morning sector, prevailing velocity propagation is westward influenced by the solar terminator effect and it also depends on the season: during winter the dominant propagation velocity is north-westward and during summer is south-westward. In the evening and night sector, the prevailing propagation velocity is southward suggesting auroral origin of the disturbance. The higher activity at night-time might be the result that neutral winds favour equatorward propagation at night whereas at day might prevent to propagate to low latitudes.

Similar behaviour has been found for high and low solar activity with the difference that during summer at low solar activity, large occurrence of sporadic E layer happens during day time. Then, ionospheric data experience large data gaps at the F region because of screening of the Es (Es Blanketing effect). This results in a poor statistic under such a conditions for daytime summer low solar activity and the number of detected LSTID is lower.

How to cite: Blanch, E., Segarra, A., Altadill, D., Paznukhov, V., and Juan, J. M.: Large Scale TIDs climatology over Europe using HF Interferometry method, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7842, https://doi.org/10.5194/egusphere-egu2020-7842, 2020.

D3016 |
Ruyi Peng and Liping Fu

As a space-based optical remote sensing method, Far-ultraviolet Ionospheric Photometer with small size, low power consumption, high sensitivity is an important means to detect physical parameters of the ionosphere. Using the Far-ultraviolet Ionospheric Photometer to detect the intensity of ionospheric 135.6nm night airglow can obtain the ionospheric TEC, F2 layer peak electronic density(NmF2), which can be used to study the information on changes in ionospheric space environment,and the impact of the ionosphere on the radio communications, etc.; The ionospheric 135.6nm day airglow and the LBH radiation radiance can be used to obtain the ionospheric O / N2 ratio information, which can be used to study the space weather events and monitor the electromagnetic environment changes in the Earth's space. The FY3-D Ionospheric Photometer(IPM), launched on November 15, 2017, has a detection sensitivity which is greater than 150 counts / s / Rayleigh and a spatial field of view of 1.6 × 3.5 ° with high horizontal spatial resolution that will help to achieve the fine detection of the ionosphere. This report will analyze the FY3-D IPM detection results.At the same time,the report will introduce our research team’s work on the development and application of other payloads in the far ultraviolet band

How to cite: Peng, R. and Fu, L.: Far-ultraviolet Ionospheric Photometer, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18779, https://doi.org/10.5194/egusphere-egu2020-18779, 2020.

D3017 |
Chaosong Huang

Geomagnetic storms cause the largest disturbances in the ionosphere-thermosphere system. We use measurements with satellites and ground based radars to study storm-induced variations in ionospheric plasma drift, ion density, and ion composition at low latitudes. It is found that the storm-time change of ion drift velocity in the equatorial ionosphere can reach 200-300 m/s, the change of ion density can be one or two orders of magnitude, and the change of ion composition can be 50-80%. These extremely large changes in the ionosphere can last for several hours or even a few days during the main and recovery phases of magnetic storms. The longitudinal, latitudinal and hemispheric differences of storm-time ionospheric disturbances are analyzed from measurements of multiple satellites or radar chain. Very long, continuous penetration of interplanetary electric fields to the equatorial ionosphere for 6 or even 14 hours are observed, and the time when disturbance dynamo electric fields become dominant is identified. The interplay of penetration, shielding, and disturbance dynamo electric fields in the storm-time ionosphere will be addressed. Mechanisms responsible for storm-time ionospheric dynamics will be discussed.

How to cite: Huang, C.: Ionospheric dynamic and coupling processes during geomagnetic storms, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10498, https://doi.org/10.5194/egusphere-egu2020-10498, 2020.

D3018 |
| Highlight
Valentina Zharkova, Simon Shepherd, and Elena Popova

In this paper we explore the millennial oscillations (or Hallstatt cycle) of the baseline solar magnetic field, total solar irradiance and baseline terrestrial temperature detected from Principal Component Analysis of the observed solar background magnetic field. We confirm the existence of these oscillations with a period of 2100-2200 years with the similar oscillations detected in carbon 14C isotope abundances and with wavelet analysis of solar irradiance in the past 12 millennia indicating the presence of this  millennial period among a few others. We also test again the idea expressed in our paper Zharkova et al, 2019 that solar inertial motion (SIM) can cause these millennial variations because of a change of the distance between the Sun and Earth. In this paper we use the S-E distance derived from the current JPL ephemeris, finding that currently starting from the Maunder minimum the Sun-Earth  distance is reducing by 0.00025 au per 100 years, or by 0.0025 au per 1000 years.. We present the estimation of variations of solar irradiance caused by this variation of the S-E distance caused by solar inertial motion (SIM) demonstrating these variations to be closely comparable with the observed variations of the solar irradiance measured by the SATIRE payload. We also estimate the baseline temperature variations since Maunder Minimum caused by the increase of solar irradiance caused by the recovery from grand solar minimum and by reduction of the S-E distance caused by  SIM. These estimations show that the Sun will still continue moving towards the Earth in the next 700 years that will result in the increase of the baseline terrestrial temperature by up to 2.5◦C in 2700. These variations of solar irradiance will be over-imposed by the variations of solar activity of 11 cycles and the two grand solar minima occurring in 2020-2053 and 2370-2415 caused by the double dynamo actions inside the Sun.

How to cite: Zharkova, V., Shepherd, S., and Popova, E.: Millennial solar irradiance forcing (Hallstatt’s cycle) in the terrestrial temperature variations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11107, https://doi.org/10.5194/egusphere-egu2020-11107, 2020.

D3019 |
Daniel Billett, Kathryn McWilliams, and Mark Conde

In this study, the behaviour of both E and F-region neutral winds are examined in the vicinity of intense R1 and R2 field-aligned currents (FACs), measured by AMPERE. This is achieved through the dual sampling of both the green (557.5nm) and red (630nm) auroral emissions, sequentially, from a ground based Scanning Doppler Imager (SDI) located in Alaska.

With the addition of plasma velocity data from the Super Dual Auroral Radar Network (SuperDARN) and ionospheric parameters from the Poker Flat Incoheerent Scatter Radar (PFISR), we assess how the large closure of Pedersen currents (implied by the strong FACs) modifies the spatial and temporal structure of the neutral wind at different altitudes. We find that the thermosphere becomes significantly height dependent, which could indicate a broader altitude range where the Pedersen conductivity is more important during intense FAC closure.

How to cite: Billett, D., McWilliams, K., and Conde, M.: The Role of Field-Aligned Current Closure on the E and F-Region Coupled Thermosphere-Ionosphere , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11369, https://doi.org/10.5194/egusphere-egu2020-11369, 2020.

D3020 |
Anita Kullen, Simon Thor, and Lei Cai

Most models predict that transpolar arcs (TPAs) occur simultaneously in both hemispheres. Conjugate TPAs are expected to appear in the northern and southern hemisphere on opposite oval sides. However, several observational studies have shown that this is not always the cases. It has been suggested that IMF Bx and/or the Earth dipole tilt may be responsible for non-conjugate TPAs. During strongly negative IMF Bx and/or positive Earth dipole tilt a TPA is expected to occur only in the northern hemisphere (for positive Bx and/or negative dipole tilt only in the southern hemisphere).

In the present work we revisit this question by investigating three previously published and one new TPA dataset regarding the influence of IMF Bx and Earth dipole tilt on interhemispheric TPA occurrence. The results show, the Earth dipole tilt has no statistical effect on TPA conjugacy while IMF Bx may have a small influence. However, this influence is much smaller than previously reported, when normalizing the IMF Bx distribution during TPAs with the average IMF Bx distribution in the solar wind during the time period covered by the respective dataset.

In the second part of this study we present results from the new TPA dataset, which is based on three months of SUSSI DMSP images. Arc location and IMF conditions during conjugate and non-conjugate TPAs are discussed in detail and possible reasons for non-conjugate TPA events are discussed.

How to cite: Kullen, A., Thor, S., and Cai, L.: Interhemispheric conjugacy of transpolar arcs, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11602, https://doi.org/10.5194/egusphere-egu2020-11602, 2020.

D3021 |
Iurii Cherniak, Wenbin Wang, and Irina Zakharenkova

During low solar activity periods, geomagnetic disturbances still occur and impact the Earth’s ionosphere. In such conditions, even comparatively weak disturbances can lead to a noticeable ionospheric response. In particular during the extended solar minimum of the 23rd solar cycle, the October 11, 2008 geomagnetic storm of moderate intensity (Dst = -50 nT, maximum Kp=6) caused strong positive ionospheric disturbances. At midlatitudes, the storm-induced enhancement in total electron contain (TEC) exceeded by two times the normal quite time day-to-day variability and the strong density enhancement was registered in the topside ionosphere.

Using a combination of the ground-based and low-Earth-orbit (LEO) observations (ground-based GNSS networks, LEO RO COSMIC, in-situ and onboard GPS CHAMP and Swarm measurements, space-based optical observations), we examined features of ionospheric responses to several weak-to-moderate geomagnetic storms occurred at low solar activity periods of the 23rd and 24th solar cycles (2008 and 2019 years respectively). The ionospheric response was analyzed in terms of the storm-time TEC changes, large and medium scale travelling ionospheric disturbances generation, and auroral plasma irregularities intensity and location. The prominent features obtained were an intensification of ionospheric irregularities occurrence at sub-auroral latitudes and an equatorward expansion of the auroral irregularities oval, differences of TEC variations from quite-time variability, response of the topside ionosphere, and TIDs generation.

The first-principle TIEGCM simulations with a comprehensive data-model comparison was carried out to specify the main drivers responsible for the observed ionospheric responses.

This work is supported by the NASA LWS grant NNX15AB83G.

How to cite: Cherniak, I., Wang, W., and Zakharenkova, I.: Features of ionospheric responses to geomagnetic storms of low solar activity period, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12208, https://doi.org/10.5194/egusphere-egu2020-12208, 2020.

D3022 |
Kun Li, Matthias Förster, Zhaojin Rong, Stein Haaland, Elena Kronberg, Jun Cui, Lihui Chai, and Yong Wei

When the geomagnetic field is weak, the small mirror force allows precipitating charged particles to deposit energy in the ionosphere. This leads to an increase in ionospheric outflow from the Earth’s polar cap region, but such an effect has not been previously observed because the energies of the ions of the polar ionospheric outflow are too low, making it difficult to detect the low-energy ions with a positively charged spacecraft. In this study, we found anti-correlation between ionospheric outflow and the strength of the Earth’s magnetic field. Our results suggest that the electron precipitation through the polar rain can be a main energy source of the polar wind during periods of high levels of solar activity. The decreased magnetic field due to spatial inhomogeneity of the Earth’s magnetic field and its effect on outflow can be used to study the outflow in history when the magnetic field was at similar levels.

How to cite: Li, K., Förster, M., Rong, Z., Haaland, S., Kronberg, E., Cui, J., Chai, L., and Wei, Y.: The Polar Wind Modulated by the Spatial Inhomogeneity of the Strength of the Earth’s Magnetic Field, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12474, https://doi.org/10.5194/egusphere-egu2020-12474, 2020.

D3023 |
Catalin Negrea, Costel Munteanu, and Marius Echim

The solar wind is one of the main drivers for the thermosphere-ionosphere, affecting both long-term trends and short-term variability. In this study, we investigate the global ionospheric impact of high-speed solar wind streams/corotating interaction regions (HSS/CIR). Ten such events are identified between December 1st 2007 and April 16th 2008, based on solar wind speed, density and magnetic field measurements. Each event triggered a geomagnetic storm, highlighted by the temporal evolution of the SYM-H and AE geomagnetic indices. The ionospheric response to these storms is investigated using 28 globally distributed ionosonde stations, providing NmF2 and hmF2 measurements. Spectral peaks associated with 27-, 13- and 9-day periodicities are identified at most locations, highlighting the global nature of the ionospheric response. The amplitude of the ionospheric diurnal variability is also shown to vary, to a large extent correlated with the HSS/CIR induced geomagnetic storms.

How to cite: Negrea, C., Munteanu, C., and Echim, M.: Global Ionospheric Response to CIR/HSS Induced Geomagnetic Storms, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16400, https://doi.org/10.5194/egusphere-egu2020-16400, 2020.

D3024 |
Claudia Borries, Arthur Amaral Ferreira, Chao Xiong, Renato Alves Borges, Jens Mielich, and Daniel Kouba

Large Scale Travelling Ionospheric Disturbances (LSTIDs) are a frequent phenomenon during ionospheric storms, indicating strong electrodynamic processes in high latitudes. LSTIDs are signatures of Atmospheric Gravity Waves (AGW) observed in the changes of the electron density in the ionosphere. During ionospheric storms, large scale AGWs are often generated in the vicinity of the auroral region, where sudden strong heating processes take place.

Many LSTIDs are observed during the ionosphere storm during the September 2017 Space Weather event. In this presentation, the LSTID occurrence on 8th September 2017 is analysed in more detail, based on a TID detection method using ground based Global Navigation Satellite System (GNSS) measurements. Fast LSTIDs are observed in midlatitudes between 0-3 UT and 13-16 UT. Slow LSTIDs are observed between 3-12 UT. A significant strong wave-like TEC perturbation occurred in high latitudes at noon, which vanished at around 50°N. A strong single LSTID in mid-latitudes generated in high latitudes around 18 UT. Consulting IMAGE magnetometer data, ionosonde measurements and Swarm field aligned current measurements, strong heating processes, the extension of the Auroral oval and unusual electrodynamic processes are discussed as source mechanisms for these LSTIDs.

How to cite: Borries, C., Ferreira, A. A., Xiong, C., Borges, R. A., Mielich, J., and Kouba, D.: Properties and Generation of Large Scale Travelling Ionospheric Disturbances during 8 September 2017, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18107, https://doi.org/10.5194/egusphere-egu2020-18107, 2020.

D3025 |
Gabriel Giono, Nickolay Ivchenko, and Tima Sergienko

On February 2nd 2016 the SPIDER sounding rocket released ten Free Falling Units (FFUs) inside an active westward-travelling auroral electrojet (between 100 to 120 km altitude). Each FFUs carried four electric field probes and four Langmuir probes, respectively on 2 and 1-meter wire booms, as well as a 3-axis fluxgate magnetometer, a gyroscope, an accelerometer and a GPS recorder. The main scientific objective of the project was to study waves and instabilities on various spatial scales, in particular the Farley-Buneman instability, as well as providing an in-situ picture of plasma properties inside the aurora.

Six FFUs were successfully recovered after landing and, despite some mechanical issues on some units, the recorded data showed promising results. Some of these results will be discussed in this presentation, namely (i) the electron density and temperature profiles from two FFUs compared to the incoherent scatter radar measurements from the EISCAT facility, (ii) the hints of different turbulence regimes along the flight seen in the electron density, (iii) the search for Farley-Buneman instability in the electric field data via wavelet analysis, (iv) the observation of electric field waves propagating between two FFUs and the comparison with ground-based observation of the aurora from the ALIS multi-camera system, and finally (v) a global comparison between perturbations seen in the electric field, magnetic field and plasma density and temperature on two FFUs.

These results demonstrated the potential of multi-point in-situ measurements for understanding multi-scale processes in auroras, and preliminary results from the reflight of the rocket to be happening in February 2020 will also be briefly presented.

How to cite: Giono, G., Ivchenko, N., and Sergienko, T.: Investigating waves and instabilities in the auroral E region via multi-points in-situ from the SPIDER sounding rockets, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20811, https://doi.org/10.5194/egusphere-egu2020-20811, 2020.

D3026 |
Yaqi Jin, Andres Spicher, Magnus Ivarsen, Jøran Moen, and Lasse Clausen

Polar cap patches/tongue of ionization are believed to be the dominant space weather phenomena in the high-latitude ionosphere as they are associated with significant plasma irregularities. These irregularities can greatly degrade satellite-based communication and navigation systems that rely on trans-ionospheric signals. Due to the practical need for a more reliable space weather forecasting system, the plasma structuring of these phenomena are an active area of research in recent years. In the study, we present a case of a tongue of ionization that was formed due to the transport of the high-density plasma from the dayside sunlit ionosphere into the dark polar cap. The tongue of ionization was probed by the first Norwegian scientific satellite NorSat-1 in noon-midnight orbits. Among other payloads, NorSat-1 carries the multi-needle Langmuir probe (m-NLP) system that is capable of measuring electron density at a rate up to 1 kHz. The electron density measurement shows significant irregularities at all scales along the profile of the tongue of ionization. In the dayside auroral oval, the electron density is associated with clear mesoscale (20-80 km) density enhancements, which are likely caused by structured auroral precipitations. We also use data from other satellites (e.g., Swarm and DMSP) to support observations from NorSat-1.

How to cite: Jin, Y., Spicher, A., Ivarsen, M., Moen, J., and Clausen, L.: High-resolution measurements of plasma entry into the polar cap: indication of plasma structuring, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21560, https://doi.org/10.5194/egusphere-egu2020-21560, 2020.

D3027 |
Theresa Rexer, Björn Gustavsson, Thomas Leyser, and Mike Rietveld

High frequency (HF) enhanced ion line spectra as a response to magnetic field aligned HF pumping of the polar ionosphere in an O-mode polarization can be observed at the top and bottomside F-region ionosphere under certain conditions. The European Incoherent Scatter (EISCAT) UHF radar was directed in magnetic zenith on 18th and 19th October 2017 while stepping the pump frequency of the EISCAT Heating facility across the double resonance frequency of the fourth harmonic of the electron gyrofrequency and the local upper hybrid frequency, in a 2-min-on, 2-min-off pump cycle, stepping both upward and downward in frequency. We present observations of two separate cases of topside HF enhanced ion lines (THFIL). THFIL simultaneous to bottomside HFIL (BHFIL) and conditioned by the relative proximity to the double resonance frequency, consistent with previous observations \citep{Rexer2018} were observed for heating pulses on 19th October. Recurring THFIL with a second set of characteristics were observed on 18th October, appearing independently from BHFIL and possibly conditioned by the proximity of the topside double resonance frequency. Propagation of the pump wave to the topside ionosphere is consistent with L-mode wave propagation facilitated by density striations in the plasma. We consider the conditions for the occurrence of THFIL for two cases/types of observations. 

How to cite: Rexer, T., Gustavsson, B., Leyser, T., and Rietveld, M.: Conditions for topside ionline enhancements , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22534, https://doi.org/10.5194/egusphere-egu2020-22534, 2020.