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ST3.3

Towards better understanding of the ionospheric plasma irregularities and scintillations

Plasma density irregularities can occur at all latitudes in the Earth’s ionosphere. However, the onset and evolution of these irregularities as well as their influence on the radio wave signals continue to be unsolved scientific questions. The various proposed generation mechanisms, including instability growth rates and seeding processes, are strongly coupled to the neutral atmosphere and magnetospheric dynamics, making the forecasting of ionospheric irregularities much more challenging. Recent observations from ground- and space-based measurements, as well as new innovative data analysis and modeling techniques, e.g., data assimilation and machine learning, have the potential to advance our understanding of the ionospheric irregularities. Studies that focus on the observation, modeling and prediction of plasma irregularities of different scales are welcome at this session. The mitigation of negative effects and recent developments to forecast scintillation effects on Global Navigation Satellite or other communication systems are also of high interest.

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Convener: Chao XiongECSECS | Co-conveners: Lucilla Alfonsi, Jens Berdermann, Yaqi Jin, Jeffrey Klenzing

vPICO presentations

| Fri, 30 Apr, 15:30–17:00 (CEST)

vPICO presentations: Fri, 30 Apr

Chairpersons: Chao Xiong, Lucilla Alfonsi, Yaqi Jin

15:30–15:40

EGU21-9441

solicited

Global Ionospheric Scintillation Model: current status and further development strategies

Dmytro Vasylyev, Yannick Beniguel, Volker Wilken, Martin Kriegel, and Jens Berdermann

When a electromagnetic wave propagates through a random inhomogeneous medium, scattering by the refractive index inhomogeneities can lead to a wide variety of phenomena that have been the subject of extensive study and modelling. The Global Ionospheric Scintillation Model (GISM) is primarily intended to model the phenomena relevant for the GNSS applications and provides the amplitude and phase scintillation indices. Due to the three dimensional nature of the GISM model it is capable to describe a variety of communication geometries such as satellite-ground station or satellite-satellite communication link. Moreover, it can calculate the scintillation maps at specific altitude allowing to obtain the 3D picture of scintillation.

Recently the GISM model has been handed over to the newly established DLR Institute of Solar-Terrestrial Physics. Since then the model underwent several modernization steps. For example, the programming paradigm has been changed to the object-oriented one in order to bring more flexibility into the code. In the present contribution we present the first results of our works and discuss strategies for further development, extension, and validation of the GISM.

How to cite: Vasylyev, D., Beniguel, Y., Wilken, V., Kriegel, M., and Berdermann, J.: Global Ionospheric Scintillation Model: current status and further development strategies, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9441, https://doi.org/10.5194/egusphere-egu21-9441, 2021.

15:40–15:42

EGU21-1883

Research Progresses of Ionospheric Plasma Irregularities from the Ground–Based Airglow Network in China

Jiyao Xu, Wei Yuan, Kun Wu, and Longchang Sun

China, from north to south, spans from the middle latitudes to the low latitude both in geographic latitude and geomagnetic latitude. And China has a variety of topography environment, which including high lands, plains, seas, and long coasts. To better understand topographic and latitudinal effects on the mesosphere and thermosphere and features of ionospheric plasma irregularities at various latitudes in China, we have established a ground-based airglow network in China gradually since 2010, which consists of 16 stations. This network almost cover China, which focuses on two airglow layers: the OI (~250 km) and OH (~87 km) airglow layers. The observations from OI airglow layers provide convenience to systematically investigate the morphologic feature and evolution of ionospheric plasma irregularities over China. Based on the airglow network observations, we mainly report some important research results of ionospheric plasma irregularities in recent years. These findings include (1) statistical characteristic of equatorial plasma bubble (EPB) over China, (2) the influences of severe extreme weather events on the ionosphere, (3) interaction between medium-scale traveling ionospheric disturbance (MSTIDs) and ionospheric irregularity, and (4) some new phenomena of ionospheric irregularities.

How to cite: Xu, J., Yuan, W., Wu, K., and Sun, L.: Research Progresses of Ionospheric Plasma Irregularities from the Ground–Based Airglow Network in China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1883, https://doi.org/10.5194/egusphere-egu21-1883, 2021.

15:42–15:44

EGU21-1881

Equatorial Ionospheric Irregularities Observed by COSMIC 2 and GOLD Missions

Qian Wu, John Braun, William Schreiner, Sergey Sokolovskiy, Iurii Cherniak, Irina Zakharenkova, Nick Pedatella, Min-yang Chou, and Doug Hunt

Equatorial ionospheric irregularities is an important space weather phenomenon, which can disrupt GNSS and communication systems. COSMIC 2 GNSS RO observations are affected via scintillations in signal amplitudes and phases. At the same time, we can use these scintillations to monitor and geolocate the ionospheric irregularities, which are of great value to the space weather services. Geolocation of the irregularities based on the RO signals is difficult, as any irregularities along the line between the GNSS and RO satellite can cause scintillation. Several geolocation methods are known. A back propagation (BP) method to geolocate the irregularities originally developed in 2001 and applied for GPS/MET RO data is being modified and applied for COSMIC 2 scintillation data. Because the equatorial irregularities are often associated with plasma bubbles, which are visible to the NASA UV imager GOLD, we have been using the GOLD images to validate the BP geolocation method. In this presentation, we will show the progress of recent validation effort of the BP geolocation method by comparing the COSMIC 2 geolocated irregularities with plasma bubbles in GOLD UV observations. Though, GOLD observations are only available in the American sector, COSMIC 2 observations can be used geolocate ionospheric irregularities throughout the equatorial and low latitudes

How to cite: Wu, Q., Braun, J., Schreiner, W., Sokolovskiy, S., Cherniak, I., Zakharenkova, I., Pedatella, N., Chou, M., and Hunt, D.: Equatorial Ionospheric Irregularities Observed by COSMIC 2 and GOLD Missions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1881, https://doi.org/10.5194/egusphere-egu21-1881, 2021.

15:44–15:46

EGU21-7319

On the phase detrending to disentangle refraction and diffraction on GNSS signals: a case study over Antarctica

Luca Spogli, Hossein Ghobadi, Antonio Cicone, Lucilla Alfonsi, Claudio Cesaroni, Nicola Linty, Vincenzo Romano, and Massimo Cafaro

We investigate the reliability of the phase scintillation index determined by receiving Global Navigation Satellite System (GNSS) signals at ground in the high-latitudes. To the scope, we report about the capabilities of recently introduced detrending scheme based on the signal decomposition provided by the Fast Iterative Filtering (FIF) technique. This detrending scheme enables a fine tuning of the cutoff frequency for phase detrending used in the phase scintillation index definition, aimed at disentangling diffraction and refraction effects. On a single case study based on GPS and Galileo data taken by a GNSS Ionospheric Scintillation Monitor Receiver (ISMR) in Concordia Station (Antarctica), we show how the FIF-based detrending allows deriving adaptive cutoff frequencies, whose value changes minute-by-minute. They are found to range between 0.4 Hz and 1.2 Hz. This allows better accounting for diffractive effects in phase scintillation index calculation and also showing the limitations on the use of such index, being still widely used in the community, both to characterize the features of ionospheric irregularities and to adopt mitigation solutions.

How to cite: Spogli, L., Ghobadi, H., Cicone, A., Alfonsi, L., Cesaroni, C., Linty, N., Romano, V., and Cafaro, M.: On the phase detrending to disentangle refraction and diffraction on GNSS signals: a case study over Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7319, https://doi.org/10.5194/egusphere-egu21-7319, 2021.

15:46–15:48

EGU21-1897

Ionospheric F-layer scintillation observations using COSMIC and COSMIC2 GPS/GNSS radio occultation data

Lung-Chih Tsai, Shin-Yi Su, and Chao-Han Liu

The FormoSat-3/ Constellation Observing System for Meteorology, Ionosphere and Climate (FS3/COSMIC) has been proven a successful mission on performing active limb sounding of the ionosphere using the GPS radio occultation (RO) technique. The follow-on program called FS7/COSMIC2 is in progress with satellite launched on 25 June of 2019 and includes six low-Earth-orbit (LEO) satellites at 24°-inclination and ~720-km orbits to receive multi-channel (1.5GHz and 1.2GHz) GPS and GLONASS satellite signals. The FS7/COSMIC2 can provide about 5,000 GNSS RO observations per day which are increased by a factor of about 5 comparing to FS3/COSMIC and within the region from the geographic equator to the latitude at 40°. We process 1-Hz amplitude data and obtain complete limb-viewing profiles of the undersampling-S4 scintillation index to study global F-layer irregularity morphology. There are a few percent of FS3/COSMIC and FS7/COSMIC2 GPS/GNSS RO observations having >0.09 undersampling S4max values on average. However, seven identified areas Central Pacific Area, South American Area, African Area, European Area, Japan Sea Area, Arctic Area and Antarctic Area have been designated to have a much higher percentage of strong limb-viewing L-band scintillations. Generally, the F-layer scintillation climatology, namely, its variations with each identified zone, altitude, season, and local time have been documented. The large dataset from the FS3/COSMIC and FS7/COSMIC2 programs enable statistical studies on equatorial and low-latitude ionospheric irregularity and their models.

How to cite: Tsai, L.-C., Su, S.-Y., and Liu, C.-H.: Ionospheric F-layer scintillation observations using COSMIC and COSMIC2 GPS/GNSS radio occultation data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1897, https://doi.org/10.5194/egusphere-egu21-1897, 2021.

15:48–15:50

EGU21-3780

Multiple transpolar auroral arcs reveal new insight about coupling processes in the Earth’s magnetotail

Qing-He Zhang, Yong-Liang Zhang, Chi Wang, Michael Lockwood, Hui-Gen Yang, Bin-Bin Tang, Zan-Yang Xing, Kjellmar Oksavik, Larry R. Lyons, Yu-Zhang Ma, Qiu-Gang Zong, Jøran Idar Moen, and Li-Dong Xia

A distinct class of aurora, called transpolar auroral arc (TPA) (in some cases called “theta” aurora), appears in the extremely high latitude ionosphere of the Earth when interplanetary magnetic field (IMF) is northward. The formation and evolution of TPA offers clues about processes transferring energy and momentum from the solar wind to the magnetosphere and ionosphere during a northward IMF. However, their formation mechanisms remain poorly understood and controversial. We report a new mechanism identified from multiple-instrument observations of unusually bright, multiple TPAs and simulations from a high-resolution three-dimensional global MagnetoHydroDynamics (MHD) model. The observations and simulations show an excellent agreement and reveal that these multiple TPAs are generated by precipitating energetic magnetospheric electrons within field-aligned current (FAC) sheets. These FAC sheets are generated by multiple flow shear sheets in both the magnetospheric boundary produced by Kelvin-Helmholtz instability between super-sonic solar wind flow and magnetosphere plasma, and the plasma sheet generated by the interactions between the enhanced earthward plasma flows from the distant tail (less than -100 R_E) and the enhanced tailward flows from the near tail (about -20 R_E). The study offers a new insight into the complex solar wind-magnetosphere-ionosphere coupling processes under a northward IMF condition, and it challenges existing paradigms of the dynamics of the Earth’s magnetosphere.

How to cite: Zhang, Q.-H., Zhang, Y.-L., Wang, C., Lockwood, M., Yang, H.-G., Tang, B.-B., Xing, Z.-Y., Oksavik, K., Lyons, L. R., Ma, Y.-Z., Zong, Q.-G., Moen, J. I., and Xia, L.-D.: Multiple transpolar auroral arcs reveal new insight about coupling processes in the Earth’s magnetotail, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3780, https://doi.org/10.5194/egusphere-egu21-3780, 2021.

15:50–15:52

EGU21-16093

Quasi real-time monitoring of the ionosphere plasma irregularities by the records of the Swarm mission

Peter Kovacs and Balazs Heilig

The magnetic and plasma observations of Low-Earth orbit (LEO) space missions represent not only the dynamical state of the ionosphere but also the physical variations of its electromagnetically connected surroundings, i.e. of the plasmasphere and magnetosphere, as well as of their driver, the solar wind. The monitoring of the ionosphere plasma variables is therefore a big asset for the study of our space environment in broad spatial region. Within the framework of the EPHEMERIS project supported by ESA, we aim at investigating two ionosphere phenomena that exhibit close relationship to global physical processes and space weather activity. We use the magnetic and plasma records of the LEO Swarm mission. First, we investigate the temporal and spatial occurrences of the mid-latitude ionosphere trough (MIT), a typical feature of the topside sub-auroral ionosphere appearing as a few degree wide depleted zone, where electron density (Ne) drops by orders of magnitude. It is shown that the locations of MITs are excellent proxies for the detection of the plasmapause position as well as of the equatorward edge of the auroral oval. Secondly, we monitor the irregular fluctuations of the magnetic field along the Swarm orbits via their intermittent behaviour. A new index called intermittency index (IMI) is introduced for the quantitative exemplification of the spatial and temporal distribution of irregular variations at the Swarm spacecraft altitudes. The paper focuses on the introduction of the methodology of IMI time-series compilation. Since IMIs are deduced via a statistical approach, we use the 50 Hz sampling frequency magnetic field records of the mission. We show that most frequently, the ionosphere magnetic field irregularities occur at low-latitudes, about the dip equator and at high latitudes, around the auroral region. It is conjectured that the equatorial events are the results of equatorial spread F (ESF) or equatorial plasma bubble (EPB) phenomena, while the auroral irregularities are related to field-aligned currents (FAC). The ionosphere plasma irregularities may result in the distortion or loss of GPS signals. Therefore our analysis also concerns the investigation of the correlation between observed intermittent events in the ionosphere and contemporary GPS signal loss events and scintillations detected both by on-board Swarm GPS receivers and ground GNSS stations.

How to cite: Kovacs, P. and Heilig, B.: Quasi real-time monitoring of the ionosphere plasma irregularities by the records of the Swarm mission, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16093, https://doi.org/10.5194/egusphere-egu21-16093, 2021.

15:52–15:54

EGU21-1458

The influence of ionospheric neutral wind variations on the propagation of a MSTID event

Ji Luo, Jiyao Xu, Kun Wu, Wenbin Wang, Chao Xiong, and Wei Yuan

The event reports a special case of the propagation and morphology of medium scale travelling ionospheric disturbances (MSTIDs) over middle–latitude China. The MSTIDs were simultaneously observed by the all-sky imager, Swarm satellite, as well as the total electron content (TEC) from global positioning system (GPS). In addition, the MSTIDs lasted for about 6 hours of the field view of airglow imager, the continuous imagers show that the inclination angles of phase fronts were decreasing gradually during the propagation process, resulting in the propagation direction changed from southwestward to nearly westward. More interestingly, the MSTIDs began to dissipate in the airglow observation when they propagated to lower latitudes with the MSTIDs at higher latitudes still visible in the later times. The simulation results from the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) and the Fabry-Perot Interferometer (FPI) wind observations suggest that the variations of background neutral winds and the ionospheric density might play important roles in the changes of propagation direction and the dissipation of MSTIDs.

How to cite: Luo, J., Xu, J., Wu, K., Wang, W., Xiong, C., and Yuan, W.: The influence of ionospheric neutral wind variations on the propagation of a MSTID event, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1458, https://doi.org/10.5194/egusphere-egu21-1458, 2021.

15:54–15:56

EGU21-10770

Spectral Properties of Kilometer-Scale Equatorial Irregularities as Seen by the Swarm Satellites

Stephan C. Buchert, Sharon Aol, and Edward Jurua

The three Swarm satellites have crossed the equator close to 80000 times each, and a large database of plasma density measurements at spatial resolution up to 500 m is available. This allows to investigate spectral properties of often seen irregularities at scale sizes of kilometers and tens of kms at heights between about 410 and 480 km above sea level. In this range of altitudes electrons are nearly completely magnetized, and ions slightly demagnetized. Therefore the irregularities could be anisotropic with a tendency to be aligned with respect to B. The satellite crossings are close to the geodetic north-south direction. Consequently the tracks of density measurement/satellite orbit have an angle with B between 0 and up to 60 deg within magnetic latitudes +/-30 degrees. Spectral properties that we have investigated are the slope of the power over wavelength, index p, and the structure function of the density. The spectral index p indicates more shallow spectra at larger angles with respect to B, in agreement with the expectation above. The spectra are also more shallow near the crests of the equatorial ionization anomaly at +/-15-20 deg magnetic latitude. This could be caused by a larger linear growth rate at these locations, which might in turn be caused by a less horizontal B.

How to cite: Buchert, S. C., Aol, S., and Jurua, E.: Spectral Properties of Kilometer-Scale Equatorial Irregularities as Seen by the Swarm Satellites, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10770, https://doi.org/10.5194/egusphere-egu21-10770, 2021.

15:56–15:58

EGU21-3832

ECS

Strong equatorial plasma bubble associated with prominent TEC enhancement observed at mid-latitude ionosphere under the quiescent condition

Fuqing Huang, Jiuhou Lei, and Chao Xiong

15:58–16:00

EGU21-6599

Farley Buneman instabilities in the Auroral region: Continuous kinetic and hybrid simulations.

Enrique Rojas and David Hysell

Farley-Buneman instabilities generate a spectrum of field-aligned plasma density irregularities in the E region. Although fully kinetic particle-in-cell simulations offer a comprehensive description of the underlying physics, its computational cost for studying non-local phenomena is tremendous. New methods based on hybrid and continuous approaches have to be explored to capture non-local physics.

In this work, we present new developments on a continuous solver of Farley-Buneman waves. We compare the performance of fully kinetic (continuous), hybrid, and fluid models. Furthermore, we investigate phase speed saturation, wave turning effects, and dominant wavelengths and assess how well these correspond to radar measurements. Finally, we describe some initial attempts at constructing simple surrogate models to capture the dominant microphysics of these simulations.

How to cite: Rojas, E. and Hysell, D.: Farley Buneman instabilities in the Auroral region: Continuous kinetic and hybrid simulations., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6599, https://doi.org/10.5194/egusphere-egu21-6599, 2021.

16:00–16:02

EGU21-3959

ECS

The GPS Scintillations and TEC Variations in Association with A Polar Cap Arc

Yong Wang, Zheng Cao, Zan-Yang Xing, Qing-He Zhang, Periyadan T. Jayachandran, Kjellmar Oksavik, Nanan Balan, and Kazuo Shiokawa

16:02–16:04

EGU21-1864

ECS

The evolution of complex Es observed by multi instruments over low-latitude China

Wenjie Sun, Baiqi Ning, Lianhuan Hu, Xiukuan Zhao, and Guozhu Li

Early and recent observations suggested that E-region field aligned irregularities (FAIs) related closely to the sporadic E (Es) layer of the ionosphere. The Sanya (18.3 ºN, 109.6 ºE) very high frequency (VHF) radar can operate at ionospheric irregularities mode for the detection of 3-m scale FAIs. The development of a portable digital ionosonde (PDI) which is collocated with the Sanya VHF radar can operate with temporal periods down to 1 minute, facilitating the capability of capturing the fast evolution of Es structures. But the low spatial resolution of the two kinds of instruments makes it difficult to depict the horizontal morphology of the Es structures and E-region FAIs. Since the capability of ground-based GNSS in strong Es detection was presented, it serves as a perfect supplement for the investigation of E region of the ionosphere. So comprehensive observation with multi kinds of instruments makes it possible to reveal the relationship and mechanisms of Es and E-region FAIs.

A complex daytime sporadic E (Es) case with extremely high critical frequency (foEs) was observed over the low latitude of China on 19 May 2018. Simultaneous observational results from two very high frequency (VHF) radars, two ionosondes, and multiple Global Navigation Satellite System total electron content and scintillation receivers are analyzed to investigate the evolution of the complex Es occurrence, which consisted of a relatively weak ambient Es layer (foEs < 8 MHz) and band-like strong Es structures (foEs > 17 MHz) drifting from higher latitude. The strong Es structures elongated more than 500 km in the northwest-southeast direction, drifted southwestward at a speed of ~65 m/s. VHF radar backscatter echoes were generated when the strong Es structures passed the radar field of view, with different echo patterns due to different radar and antenna configurations. No VHF radar backscatter echo was associated with the ambient Es layer.

How to cite: Sun, W., Ning, B., Hu, L., Zhao, X., and Li, G.: The evolution of complex Es observed by multi instruments over low-latitude China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1864, https://doi.org/10.5194/egusphere-egu21-1864, 2021.

16:04–16:06

EGU21-5554

ECS

Comparisons Between E-region Coherent Scatter and Swarm-E Fast Auroral Imager Measurements

Devin Huyghebaert, Kathryn McWilliams, Glenn Hussey, Andrew Howarth, Stephanie Erion, and Paige Rutledge

The Ionospheric Continuous-wave E-region Bistatic Experimental Auroral Radar (ICEBEAR) is a VHF coherent scatter radar that makes measurements of the E-region ionosphere with a field of view centered on ≈ 58°N, 106°W. This overlaps with the Saskatoon SuperDARN radar field of view, providing the opportunity for multi-frequency coherent scatter radar measurements in a similar region. In conjunction with these coherent scatter radar measurements, the Swarm-E, or e-POP, satellite Fast Auroral Imager (FAI) has been used to make measurements of auroral emissions in the 650-1100 nm wavelength band over the same field of view. The primary emission species in this wavelength range are N₂, O₂, and N₂⁺, which correspond to energetic charged particle precipitation penetrating into the lower altitudes of the ionosphere. This makes the FAI a great instrument for comparison studies with E-region coherent scatter. In addition to this, the FAI is able to be slewed to a location allowing for extended conjunction windows between the imager and the coherent scatter radars. With recent advances in radar hardware and processing the temporal and spatial resolutions of these different instruments are becoming comparable (~ 1 s, 1.5 km), providing an excellent opportunity to study plasma density irregularities in the E-region ionosphere in great detail. Comparisons between the coherent scatter radar and FAI measurements are presented, providing insights into how E-region plasma density irregularities correspond to the location of auroral emissions at 650-1100 nm wavelengths.

How to cite: Huyghebaert, D., McWilliams, K., Hussey, G., Howarth, A., Erion, S., and Rutledge, P.: Comparisons Between E-region Coherent Scatter and Swarm-E Fast Auroral Imager Measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5554, https://doi.org/10.5194/egusphere-egu21-5554, 2021.

16:06–16:08

EGU21-1457

Developing Equatorial Plasma Bubbles Observed by Multi-Instrument at Dawn

Kun Wu, Jiyao Xu, Xinan Yue, Chao Xiong, Wenbin Wang, Wei Yuan, Chi Wang, Yajun Zhu, and Ji luo

16:08–16:10

EGU21-6582

Modeling and analysis of LOFAR scintillation data

Marcin Grzesiak, Mariusz Pożoga, Barbara Matyjasiak, Dorota Przepiórka, Hanna Rothkaehl, Katarzyna Budzińska, and Barbara Atamaniuk

Scintillation of beacon satellite signals or distant cosmic radio emissions can provide interesting information on the cosmic medium itself, its internal spatial structure and basic evolution characteristics. LOFAR network gives consistent scintillation data with good coverage both in time and space and for the frequency range that goes down close to the local plasma frequency (LBA) being thus sensible to ionospheric plasma irregularities. LOFAR Scintillation measurements in the LBA range exhibit very interesting morphologies. Based on scintillation simulations using the phase screen method, including multiple scattering and refraction, we try to untangle the information contained in the full range (time, space, frequency) of LOFAR data and verify a number of hypotheses about the local structure of the ionosphere and its evolution.

How to cite: Grzesiak, M., Pożoga, M., Matyjasiak, B., Przepiórka, D., Rothkaehl, H., Budzińska, K., and Atamaniuk, B.: Modeling and analysis of LOFAR scintillation data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6582, https://doi.org/10.5194/egusphere-egu21-6582, 2021.

16:10–16:12

EGU21-7964

ECS

Identifying evolving/non-evolving plasma bubbles from SWARM observations

Chinmaya Nayak, Stephan Buchert, and Bharati Kakad

Equatorial plasma bubbles (EPBs) are generally caused due to the Rayleigh–Taylor instability. During the initial phase of the growth of the instability, the bubbles are associated with perturbation electric and magnetic fields. We call this the evolving (active) phase of the EPB. Over time, these electric field fluctuations decay in amplitude and the bubble, embedded in the neutral atmosphere, drifts eastward without much temporal evolution. We call this the non-evolving phase. Both phases can be distinguished in ground based VHF spaced receiver scintillation observations. In the evolving phase, the cross correlation between the signals from the two receivers is significantly less than one because of rapidly evolving perturbation electric fields. However, after some time (~2 hours) as the perturbation electric field decays, the cross correlation reaches almost 1 implying very slow temporal changes. This technique is applied to identify fresh generation of post-midnight plasma bubbles during magnetically disturbed conditions. From in situ satellite observations, the EPBs are generally identified as sudden depletion from background electron density, associated with magnetic fluctuations. In fact, the plasma bubble index produced from data of the ESA Swarm mission utilizes this same criteria of concurrent density depletions and magnetic fluctuations to identify the plasma bubbles. However, it is not so straightforward to distinguish evolving and non-evolving phases of the plasma bubbles in the SWARM plasma and magnetic observations. We look into near simultaneous in situ observations of SWARM and ground based VHF spaced receiver scintillation to identify a standard criteria for distinguishing evolving/non-evolving bubbles in SWARM observations. The results suggest that the presence/absence of magnetic fluctuations associated with the depletion in electron density can be used as a criteria for evolving/non-evolving bubbles. Ideally, the electric and magnetic field fluctuations should be present simultaneously and as a result should decay simultaneously. We have looked into one year (2014) of SWARM observations of EPBs and VHF spaced receiver scintillation data from Indian equatorial station Tirunelveli. A few case studies during both magnetically quiet and disturbed conditions are discussed.

How to cite: Nayak, C., Buchert, S., and Kakad, B.: Identifying evolving/non-evolving plasma bubbles from SWARM observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7964, https://doi.org/10.5194/egusphere-egu21-7964, 2021.

16:12–16:14

EGU21-1059

Characteristic of daytime F-region backscatter plume structures over low latitude of China

Haiyong Xie

Ionospheric F‐region irregularity backscatter plumes are commonly regarded as a nighttime phenomenon at equatorial and low latitudes. At daytime, there are very few reported cases of F‐region backscatter echoes. It is still not clear what caused the daytime echoes. In order to understand the occurrence of daytime F‐region echoes, we carried out an experiment with Sanya VHF radar (18.4°N, 109.6°E, dip lat. 12.8°N) during November 2016 to August 2020. Some basic characteristics were released: (1) The daytime F‐region echoing structures have an unexpected high occurrence in June solstice of solar minimum. (2) The echoing structures could appear at any time during 0700–1800 LT, with a maximum occurrence around 0900 LT. (3) The echoing structures appeared mostly above 350 km altitude, extending up to 650 km or more (F region topside) with apparent westward drifts at times. Radar interferometry and ICON satellite in situ results show that the daytime F‐region echoes were from plume structures consisting of field‐aligned irregularities. It is suggested that the plume structures could be remnants of equatorial plasma bubble (EPB) irregularities generated on the previous night around 100–125°E. They rise to high altitudes and drift zonally together with background plasma, causing the daytime F‐region backscattering structure over Sanya. With simultaneous observations of several VHF radars at different locations, satellite in-situ measurements and/or EPB model, the dynamics of daytime F-region backscatter plume structures could be better understood in the future.

How to cite: Xie, H.: Characteristic of daytime F-region backscatter plume structures over low latitude of China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1059, https://doi.org/10.5194/egusphere-egu21-1059, 2021.

16:14–16:16

EGU21-8674

ECS

TEC and Scintillations in the Ionosphere above Greenland

Sarah Beeck, Anna Jensen, and Per Knudsen

Global Navigation Satellite System (GNSS) signals are affected by the media of the ionosphere when traversing it. Therefore, near real-time monitoring of the ionosphere and its scintillation can be an advantage for GNSS users. There can be strong phase scintillation in the Arctic region, however, there is no continuous real-time monitoring of the ionosphere above Greenland at the moment. This project investigates possibilities for real-time monitoring of the ionosphere above Greenland, based on data from geodetic GNSS stations. The novelty of the work is the application of the kriging method as basis for rate of total electron content index (ROTI) maps in the Arctic.

The GNSS data analyzed in this project is from seven selected GNSS receivers that are part of the Greenland GPS Network (GNET). The data is used for computing the phase scintillation index ROTI, which is then used for mapping the scintillation activity. First the spatial data coverage was examined to investigate the possibility of visualizing the ROTI values spatially. Further, the kriging and natural neighbor methods were tested for interpolating ROTI above Greenland.

In the project there were some large spatial data gaps, caused by the sparse distribution of the GNSS receiver stations. A relation between high ROTI values and low elevation angles was shown, and this relation was more prominent at geomagnetically quiet times. This indicated that a higher elevation cut-off angle might have been useful for the mapping if more data had been available. The test of the interpolation methods lead to the conclusion that kriging provided slightly better maps than the natural neighbor method at geomagnetically active times, while natural neighbor might be preferable at geomagnetically quiet times. Finally, it was found that receivers at all of the tested latitudes were affected by ionospheric phase scintillation, this was seen as an increase in the amount of cycle slips.

The conclusions drawn from this project can help indicate what the next step should be on the path towards real-time monitoring the ionosphere above Greenland. The general recommendation for future work is to install a network of GNSS Ionospheric Scintillation and TEC Monitor (GISTM) receivers in Greenland which can provide near real-time scintillation indices.

How to cite: Beeck, S., Jensen, A., and Knudsen, P.: TEC and Scintillations in the Ionosphere above Greenland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8674, https://doi.org/10.5194/egusphere-egu21-8674, 2021.

16:16–16:18

EGU21-14374

Ionospheric Scintillation observed by LOFAR PL610 station

Mariusz Pożoga, Barbara Matyjasiak, Hanna Rothkaehl, Helena Ciechowska, Marcin Grzesiak, Roman Wronowski, Katarzyna Budzińska, and Łukasz Tomasik

Due to their low intensity, ionospheric scintillations in the middle latitude region are difficult to observe. However, scintillations intensity increases at lower frequencies. Those below 90 MHz, covered by LOFAR, enable scintillation measurements in mid-latitude region. Long-term observations, with the use of PL610 station, allow the study of weak scintillation climatology, unavailable for measurement led with other methods. The developement of functional tool for the scintillation parameters analysis described in the paper enabled the study of scintillations in the mid-latitude region and future application to the data collected by LOFAR.

LOFAR PL610 station in Borowiec (23E,50N) regularly observes ionospheric scintillation using signals from the 4 strongest radio sources, members of LOFAR A-team: Cas A, Cyg A, Vir A and Tau A. The measurements are taken by LBA antennas at frequencies in the range of 10-90 MHz. Since 2018 we have collected more than 8000 hours of observations. In this work research, we present the results of the automatic s4 calculation system based on our observations. The observations are led in 4-bit mode, for 4 independent sources, with sampling of 10 Hz at 244 subbands. Sources are selected automatically depending on their visibility. Due to the fact that natural radio sources are relatively weak and beamforming is not ideal, the data are noisy. In order to improve the quality of data, the measured amplitudes are filtered and S4 index is computed for each beamlet. All processed data are stored in a database and enable in-depth analysis of scintillation behavior in the mid-latitude region.

We look at the intrinsic features of the observation: dependence on the geometry of the measurement, impact of RFI depending on the strength of the radiosource, the observation frequency then show the dependence of scintillation on the global conditions caused by space weather.

How to cite: Pożoga, M., Matyjasiak, B., Rothkaehl, H., Ciechowska, H., Grzesiak, M., Wronowski, R., Budzińska, K., and Tomasik, Ł.: Ionospheric Scintillation observed by LOFAR PL610 station, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14374, https://doi.org/10.5194/egusphere-egu21-14374, 2021.

16:18–17:00

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