ST3.4 | Open Session on the Ionosphere and Thermosphere
EDI
Open Session on the Ionosphere and Thermosphere
Convener: Dalia Buresova | Co-conveners: Daniel BillettECSECS, Tobias Verhulst, Elisabetta IorfidaECSECS, David R. Themens, Jaroslav UrbarECSECS, Magnus IvarsenECSECS
Orals
| Thu, 18 Apr, 14:00–15:45 (CEST)
 
Room 0.51
Posters on site
| Attendance Thu, 18 Apr, 16:15–18:00 (CEST) | Display Thu, 18 Apr, 14:00–18:00
 
Hall X3
Orals |
Thu, 14:00
Thu, 16:15
The Earth's ionosphere and thermosphere form a coupled system, influenced by solar activity and magnetospheric processes from above, as well as by upward propagating disturbances from the lower atmospheric layers. This open session is intended for contributions on all aspects of ionospheric and thermospheric physics, ionospheric disturbances of different origin, and their effects on modern human technologies. The session invites theoretical studies, 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 ionospheric climate. Contributions dealing with magnetospheric forcing are sought in the areas of ionospheric disturbances caused by CME- and CIR/CH HSS-related magnetic storms and substorms. New results that focus on multi-instrumental ground-based and satellite investigation of latitudinal, seasonal, and hemispheric differences in the disturbed ionospheric behaviour are especially appreciated. Also ionospheric effects from other sources, such as the solar terminator, solar eclipses, seismic activity, or human-made explosions, are welcome. As for lower atmosphere forcing, contributions are sought that focus on atmospheric waves, wave-wave and wave-mean flow interactions, atmospheric electricity and electrodynamic coupling processes.

Session assets

Orals: Thu, 18 Apr | Room 0.51

Chairpersons: Tobias Verhulst, Daniel Billett, Dalia Buresova
14:00–14:05
14:05–14:15
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EGU24-2232
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solicited
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On-site presentation
Dieter Bilitza, Vladimir Truhlik, Christina Arras, and Haris Haralambous

Sporadic E (Es) layers are a well-known ionospheric phenomenon, whose occurrence can cause anomalous propagation of radio waves utilized for communication and broadcast. Es layers are very thin layers of metallic ions such as Fe+, Mg+, and Ca+ formed  mainly by atmospheric tidal wind shears.  Their peak density exceeds the E-layer peak density and can even exceed the F-layer peak density. Because of their effect on radio waves a user needs to know when there is a high probability of Es occurrence. It is the goal of this study to develop a global model of Es occurrence probability and to make it publicly available through inclusion in the International Reference Ionosphere (IRI).

We use Es data obtained by Arras et al. (2022) from GNSS radio occultation observations from various satellites (CHAMP, Spire, KOMPSAT-5, COSMIC1 & 2, TANDEM-X, and TerraSAR-X) for the time period 2001-2022. We will briefly discuss the variation of the Es occurrence rate with latitude, longitude, local time, season, solar activity, and magnetic activity. as observed with this data base. We found that the strongest dependencies are with local time, latitude and season, while weaker ones exist with longitude and solar activity. We use spherical harmonics to describe the global expansion of the strongest influences establishing a core model. Second order influences, e.g., solar activity variations, are modelled as a perturbation on the core model. First results obtained with the new model will be presented.

References

Arras, C., Resende, L.C.A., Kepkar, A. et al. Sporadic E layer characteristics at equatorial latitudes as observed by GNSS radio occultation measurements. Earth Planets Space 74, 163 (2022). https://doi.org/10.1186/s40623-022-01718-y

 

How to cite: Bilitza, D., Truhlik, V., Arras, C., and Haralambous, H.: Modeling the occurrence probability of sporadic-E based on GNSS radio occultation data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2232, https://doi.org/10.5194/egusphere-egu24-2232, 2024.

14:15–14:25
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EGU24-5871
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ECS
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On-site presentation
Tasha Aylett, Wuhu Feng, Daniel Robert Marsh, and John Maurice Campbell Plane

Sporadic E (Es) layers are transient ionospheric phenomena that represent an important aspect of atmospheric dynamics, exerting influences on space weather and communication systems. They occur in the E region (~90-150 km) and are characterised by thin, localised layers of enhanced electron density. Their formation is linked to interactions involving atmospheric waves and tides, wind shear and/or electric field and plasma instabilities. Metal ions are tightly coupled with electrons through ionization and neutralisation processes and play a central role in the formation of Es layers1.

Recently, Wu et al. [2021]2 examined the full transport of three metal ions (Fe+, Mg+ and Na+) in the Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) - a self-consistent global model including their full neutral and ion-molecule chemistry and the injection of metals from meteoric ablation3,4. The work of Wu et al. [2021] significantly improved the modelled global distribution and seasonal dependence of the metal ions in WACCM-X; since it captures the complex interactions between numerous atmospheric components, this extended WACCM-X provides a useful framework for the study of Es layers on a global scale.

Although modelling of parameters relevant to Es layers (winds, temperatures, chemical constituents) has been carried out using whole atmosphere models2,5, modelling of Es layer occurrence has not been carried out self-consistently using a global climate model with metal ion transport. In this study we present a novel method to identify Es layers in WACCM-X with full transport of metal ions. We present a detailed account of the methodology employed for the identification of Es layers within WACCM-X and the resulting climatology of Es occurrence. The derived climatology is compared to observations from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellite6, which provides global high-resolution ionospheric observations. This comparison enables us to evaluate the performance of the model and identifies potential areas for future development.

By better understanding the complex interplay between atmospheric variability and Es layer behaviour, we aim to improve our understanding of Es layers and their role in atmospheric dynamics. The insights gained from this research advance modelling capabilities, and could support space weather forecasting and communication systems, as well as contributing to the broader understanding of Es layers and their significance in atmospheric science.

 

1. Yu, B., et al. (2021) Atmospheric Chemistry and Physics, 21(5), 4219-4230

2. Wu, J., W. Feng, H. L. i. Liu, X. Xue, D. R. Marsh, and J. M. C. Plane (2021), Atmospheric Chemistry and Physics, 21(20), 15619-15630

3. Liu, H.-L., et al. (2018), Journal of Advances in Modelling Earth Systems, 10(2), 381-402

4. Carrillo-Sánchez, J. D., J. C. Gómez-Martín, D. L. Bones, D. Nesvorný, P. Pokorný, M. Benna, G. J. Flynn, and J. M. C. Plane (2020), Icarus, 335, 113395

5. Chu, Y. H., C. Y. Wang, K. H. Wu, K. T. Chen, K. J. Tzeng, C. L. Su, W. Feng, and J. M. C. Plane (2014), Journal of Geophysical Research: Space Physics, 119(3), 2117-2136

6. https://www.cosmic.ucar.edu/global-navigation-satellite-system-gnss-background/cosmic-1

How to cite: Aylett, T., Feng, W., Marsh, D. R., and Plane, J. M. C.: Modelling sporadic E (Es) layers in WACCM-X: Presenting a new methodology for the identification of Es layers, and the resulting climatology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5871, https://doi.org/10.5194/egusphere-egu24-5871, 2024.

14:25–14:35
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EGU24-13670
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Highlight
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On-site presentation
Larry Kepko and Douglas Rowland and the GDC Instrument and IDS teams

The Geospace Dynamics Constellation (GDC) is NASA's next strategic Living With a Star mission. GDC's goals are: 1) Understand how the high-latitude ionosphere-thermosphere system responds to variable solar wind/magnetosphere forcing; and 2) Understand how internal processes in the global ionosphere-thermosphere system redistribute mass, momentum, and energy. Planned for launch by the end of the decade, GDC will use six identical observatories, each identically instrumented to fully characterize the magnetospheric drivers of the I-T system as well as the global response of the ionized and neutral gases. GDC will do this with a series of orbital configurations that will enable it to study the widest range of spatial and temporal scales to date, ranging from hundreds of kilometers and several seconds to tens of minutes, and extending through the regional to the global scale. This talk presents GDC's current status, measurement capabilities, sampling scheme, and model development efforts and show how GDC will fit into the larger Heliophysics ecosystem, by 1) obtaining critically needed scientific observations; 2) providing a source for real-time space weather and situational awareness, as well as retrospective studies to further the science of space weather; 3) serving as a "strategic hub" for other space-based and ground-based efforts that want to leverage GDC to perform complementary science.

To get the most benefit from GDC’s observations, it will be critical to identify partnerships with other research efforts in the ITM and Geospace arenas, including those utilizing space-based, ground-based, or theoretical investigations. We particularly would like to discuss with groups who are planning or considering observational campaigns during the GDC era, to find ways to leverage GDC observations to do synergistic science that could not be done otherwise.

How to cite: Kepko, L. and Rowland, D. and the GDC Instrument and IDS teams: NASA’s Geospace Dynamics Constellation—Providing the first Systematic Measurements of Global Magnetospheric Energy Inputs and Ionosphere-Thermosphere Responses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13670, https://doi.org/10.5194/egusphere-egu24-13670, 2024.

14:35–14:45
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EGU24-16449
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ECS
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On-site presentation
Björn Linder, Linda Megner, Donal Murtagh, Ole Martin Christensen, Jörg Gumbel, and Nickolay Ivchenko

MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) is a Swedish research satellite launched in 2022 targeting gravity wave activity in the mesosphere and lower thermosphere (MLT). Infrared measurements of MLT O2 A-band airglow conducted by the MATS satellite during February, March, and April reveal large-scale, global structures that significantly impact this region's dynamics. An analysis of atmospheric A-band emissions between 70 and 110 km reveals that atmospheric tides greatly influence the radiance produced in the airglow layer. This is evidenced by an equatorial maximum at local sunset and minima at 30°N and 30°S, which correspond to the various phases of the tides. Meanwhile - in the vicinity of the poles, westward propagating planetary waves dominate the measurements, including strong signals from the 16-day wave in the northern hemisphere, and the 5.5-day wave in the southern hemisphere. In this talk, we take a closer look at the individual measurements made by the satellite, illustrating the smaller-scale atmospheric structures they contain, as well as the global picture that the images make up together. 

How to cite: Linder, B., Megner, L., Murtagh, D., Christensen, O. M., Gumbel, J., and Ivchenko, N.: MATS satellite mission: Global patterns, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16449, https://doi.org/10.5194/egusphere-egu24-16449, 2024.

14:45–15:05
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EGU24-6700
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solicited
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On-site presentation
Astrid Maute, Jeffrey Forbes, Chihoko Cullens, Brian Harding, and Thomas Immel

The lower to upper atmosphere vertical coupling via atmospheric solar tides is very variable and affects the dynamics, composition and electrodynamics of thermosphere-ionosphere (TI) system. In addition, complex solar wind forcing is always impacting the high latitude region and its effects can extend to the mid- and low latitude region.  The Ionospheric Connection (ICON) explorer mission provides almost 3 years of data and an opportunity to examine the variation in the TI due to lower atmospheric and MI forcing. This is facilitated by the ICON Level4 product, the thermosphere-ionosphere-electrodynamics general circulation model (TIEGCM) driven by tides fitted to ICON observations via the Hough Mode Extension (HME) method. The effects of the upward propagating tides can be isolated by examining the difference between two TIEGCM simulations with and without tidal HME forcing at the model’s lower boundary, while the effects of solar and magnetospheric variability can be estimated by the difference to a simulation with constant solar and geomagnetic forcing.

In this presentation we use over 2 years of TIEGCM simulations to evaluate the model by comparing primarily to ICON observations and examine the captured TI variations. A special focus in our comparison will be on the neutral wind and its two-way coupling to ion drift and plasma distribution. For specific time period we will delineate the contributions due to lower atmospheric tidal forcing from the one due to solar and magnetospheric forcing and quantify the separate effects on the neutral wind, ion drift, and plasma variation.

How to cite: Maute, A., Forbes, J., Cullens, C., Harding, B., and Immel, T.: Thermosphere-ionosphere effects due to forcing from “above” and “below” as captured by TIEGCM-ICON, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6700, https://doi.org/10.5194/egusphere-egu24-6700, 2024.

15:05–15:15
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EGU24-7647
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On-site presentation
Rajesh Vaishnav, Christoph Jacobi, Erik Schmölter, Hanna Dühnen, and Mihail Codrescu

Having a comprehensive understanding of the ionosphere's irregular behavior and its response to solar activity is crucial for satellite communication and navigation applications. The sun's extreme ultraviolet (EUV) and ultraviolet (UV) radiation are the primary sources of energy for the Earth's thermosphere and ionosphere (TI). To understand the global response of TI parameters (e.g., O/N2, and the peak electron density (Nmax)) to changes in solar irradiance, various data have been used. These include the Global-Scale Observations of the Limb and Disk (GOLD) ultraviolet imaging spectrograph, solar radio flux F10.7, predictions from the Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model, and International Global Navigation Satellite System Service total electron content maps (TEC). The comparison between these measurements shows that the CTIPe model successfully reproduces the behavior of the low- and mid-latitude ionosphere during both low and high solar activity.

The study also investigated the delayed ionospheric TEC response against solar flux variations within the 27-day solar modulation. It was observed that the delay is less than one day, which was also confirmed in model simulations. Furthermore, the model simulations showed that the ionospheric time delay is significantly affected by various physical processes such as diffusion, photodissociation, solar and geomagnetic activities, and wave dynamics.

How to cite: Vaishnav, R., Jacobi, C., Schmölter, E., Dühnen, H., and Codrescu, M.: Solar activity variations in the composition of the low- and mid-latitude ionosphere-thermosphere system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7647, https://doi.org/10.5194/egusphere-egu24-7647, 2024.

15:15–15:25
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EGU24-6223
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ECS
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On-site presentation
Ben Boyde, Alan Wood, Gareth Dorrian, Francesco de Gasperin, Frits Sweijen, Maaijke Mevius, and Kasia Beser

The LOw Frequency ARray (LOFAR) is a radio telescope centred in the Netherlands. The observed impact of the ionosphere on signals from astronomical radio sources can be used to derive differential Total Electron Content (dTEC) between the lines of sight from different LOFAR stations. The dTEC derived in calibration has extremely high precision (~1 mTECu) and is available at high temporal (~4s) and spatial (baselines from ~100 m to ~100 km) resolutions. These measurements provide a new means of studying ionospheric disturbances in the mid-latitudes.

A method for identifying wave signatures in the dTEC data has been developed and shown to be capable of identifying waves with amplitudes as low as a few mTECu (Boyde et al., 2023). This method has been used to analyse over 2,500 hours of observations made as part of an astronomical survey. The statistical characteristics of the identified waves and their dependence on time of day, season, and geomagnetic activity are discussed, such as variations in dominant propagation direction. These observations extend the range of ionospheric waves that can be identified to shorter wavelengths and lower amplitudes beyond what is currently detectable using GNSS derived TEC. This method complements established techniques for detecting ionospheric waves.

Ben Boyde, Alan George Wood, Gareth Dorrian, et al. Wavelet Analysis of Differential TEC Measurements Obtained Using LOFAR, Radio Science (Under Review), 2023, doi: 10.22541/essoar.169754969.93126117/v1

How to cite: Boyde, B., Wood, A., Dorrian, G., de Gasperin, F., Sweijen, F., Mevius, M., and Beser, K.: Statistics of Small-Scale Ionospheric Waves in European Mid-Latitudes Observed Using LOFAR, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6223, https://doi.org/10.5194/egusphere-egu24-6223, 2024.

15:25–15:35
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EGU24-11681
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ECS
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On-site presentation
Sebastijan Mrak, Clayton Cantrall, Naomi Maruyama, Phil Chamberlin, Saurav Aryal, Yue Deng, and Marc Hairston

We discuss multiple observations of atmospheric dynamics during recent solar eclipses: 21 August 2017, 4 December 2021, 20 April 2023, 14 October 2023, and 8 April 2024. We use GOLD and TIMED/GUVI instruments to observe the changes in the lower thermosphere related to atmospheric oxygen O, and molecular nitrogen N2. We discuss the problematic nature of O/N2 composition estimation from brightnesses under solar obscuration conditions, and how the observations should be properly interpreted. The Ionosphere-Thermosphere (I-T) system responds to solar X-Ray and Extreme Ultra Violet (EUV) radiation, which is highly non-uniform during solar eclipses. We introduce a new model of solar eclipse obscuration and irradiance by combining the solar occultation software PyEclipse and Flare Irradiance Solar Model 2 (FISM2) -- FISM2-Eclipse. We implemented FISM2-Eclipse into the Global Ionosphere thermosphere Model (GITM) and Whole Atmosphere Model Ionosphere-Plasmasphere-Electrodynamics model (WAM-IPE) to conduct a model-data comparison. We discuss some salient features noted during the recent eclipses.

How to cite: Mrak, S., Cantrall, C., Maruyama, N., Chamberlin, P., Aryal, S., Deng, Y., and Hairston, M.: The I-T response to most recent solar eclipses: Observations and modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11681, https://doi.org/10.5194/egusphere-egu24-11681, 2024.

15:35–15:45
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EGU24-8387
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ECS
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On-site presentation
Sovan Saha, Duggirala Pallamraju, Sunil Kumar, Fazlul I. Laskar, and Nicholas M. Pedatella

Airglow emissions act as a tracer of the altitudinal region of 100 km width centred around 250 km. Various dynamical processes such as neutral, electrodynamics, and atmospheric waves modulate the atmospheric parameters, such as temperature, density, etc., of the ionosphere-thermosphere system (ITS), which vary day-to-day, season, and solar flux as well. We have carried out investigations of ITS by measuring the OI 630.0 nm (redline) nightglow emissions over Gurushikhar, Mt. Abu (24.6°N, 72.7°E, 19°N Mag), a low-latitude location, using the High Throughput Imaging Echelle Spectrograph (HiTIES). On several occasions, a bell-shaped enhancement in these emissions has been noticed around 21 local time, following the typical monotonic decrement after sunset. The cause of this enhancement in redline emissions has been explored by investigating the equatorial electrodynamics and neutral winds. The meridional winds have been obtained by using two digisondes located at equatorial and low-latitude locations. Contrary to the conventional expectation of pre-reversal enhancement bringing additional plasma over the low-latitudes to cause such enhancement, the role of meridional winds has been demonstrated in our study. The poleward winds over the low-latitudes bring additional plasma down to the redline emission altitudes, resulting in the observed enhancement in emissions. The winds at these post-sunset hours are usually equatorward, and thus, this brings the question as to what is the cause for the reversal in wind during those times. We have analysed the winds, electron densities obtained from the global free-run model of Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X) data. It has been found that higher-order tides, such as quarter-diurnal tides, play an important role in causing a reversal in meridional winds from their usual equatorward to poleward direction. This clearly explains the root cause for the variation in meridional winds during the post-sunset hours as well as the reason why the post-sunset enhancements in OI 630.0 nm nightglow occur on one night and not the next, even though the electrodynamic forcing was similar on these two occasions. These new findings will be discussed.

How to cite: Saha, S., Pallamraju, D., Kumar, S., Laskar, F. I., and Pedatella, N. M.: Higher-order Tides in the Variation of Post-sunset Meridional Winds and, consequently, OI 630.0 nm nightglow emissions over Low-latitudes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8387, https://doi.org/10.5194/egusphere-egu24-8387, 2024.

Posters on site: Thu, 18 Apr, 16:15–18:00 | Hall X3

Display time: Thu, 18 Apr, 14:00–Thu, 18 Apr, 18:00
Chairpersons: David R. Themens, Jaroslav Urbar, Elisabetta Iorfida
Open session on ionosphere and thermosphere
X3.33
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EGU24-9005
Dalia Buresova, Jaroslav Chum, Sivakandan Mani, Jens Mielich, Jaroslav Urbar, Veronika Barta, Anna Belehaki, Tobias G.W. Verhulst, David Altadill, Antoni Segara, Daniel Kouba, Marco Guerra, Petra Koucka Knizova, Zbysek Mosna, Kitti A. Berényi, Claudio Cesaroni, and Luca Spogli

It is well known that the ionosphere is a highly dynamic medium, and the electron density can vary significantly within a very short period of time at a given location. One of the reasons for the irregular variations are ionospheric signatures of Atmospheric Gravity Waves (AGWs) – Travelling Ionospheric Disturbances (TIDs). TIDs are one of the major and frequent wave-like perturbations of the ionospheric plasma. Medium scale TIDs (MSTIDs) have been described as perturbations characterized by a wavelength, period and phase speed of 50–500 km, 12–60 min and 50–400 m/s, respectively. The wave-like effects of the MSTIDs are one of the main obstacles for accurate interpolation of ionospheric corrections in a medium scale reference of the Global Positioning System (GPS) networks as the ionospheric delay is almost proportional to Total Electron Content (TEC) along the signal path and inversely proportional to the frequency squared. MSTIDs are a common phenomenon from high to low latitudes.

The main objective of the T-FORS project is the development of new validated models able to issue forecasts and alerts for TIDs several hours ahead, exploiting a broad range of observations of the solar corona, the interplanetary medium, the magnetosphere, the ionosphere and lower atmosphere. This paper presents our results on the analysis of dynamic events that trigger MSTIDs. The events identified for the purposes of the analysis were such as geomagnetic disturbances, deep tropospheric convections, earthquakes and volcano eruptions. Based on the T-FORS methodologies all available data (detrended TEC, Continuous Doppler Sounding System -CDSS measurements, Digisonde vertical and oblique soundings and gradients of the electron density, reference meteorological and seismic data) were used for this analysis. The MSTIDs occurrence was recorded and analysed and propagation pattern for these events were extracted and compared with the results of the climatological model. This comparison will support the definition of alerts criteria when the detected disturbances exceed the climatology. Physical conditions that triggered enhanced MSTID activity were also analysed to compile an inventory of parameters that can be considered as early indicators of enhanced MSTIDs.

How to cite: Buresova, D., Chum, J., Mani, S., Mielich, J., Urbar, J., Barta, V., Belehaki, A., Verhulst, T. G. W., Altadill, D., Segara, A., Kouba, D., Guerra, M., Koucka Knizova, P., Mosna, Z., Berényi, K. A., Cesaroni, C., and Spogli, L.: Analysis of MSTIDs triggered by dynamical events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9005, https://doi.org/10.5194/egusphere-egu24-9005, 2024.

X3.34
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EGU24-1288
Jan Laštovička

I use yearly average noontime foF2 from six ionospheric stations from four continents, Juliusruh, Pruhonice, Roma, Boulder, Kokubunji and Canberra over periods 1976-1995 and 1996-2014, and six solar activity indices F10.7, F30, Mg II, solar H Lyman-α flux, sunspot numbers and He II. The results reveal somewhat and sometimes even substantially different trends of foF2 when the effect of solar cycle is removed/reduced from foF2 data with different solar activity proxies. Only F30 provides for all stations and both periods the trends of the same sign (negative), other indices reveal both positive and negative trends for different stations and periods. Therefore together with results of other criteria F30 is considered to be the most reliable solar activity index for long-term studies of midlatitude foF2.

 

How to cite: Laštovička, J.: Different long-term trends of foF2 with different solar activity indices, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1288, https://doi.org/10.5194/egusphere-egu24-1288, 2024.

X3.35
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EGU24-1426
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ECS
Hanna Dühnen, Rajesh Vaishnav, Erik Schmölter, and Christoph Jacobi

The solar extreme ultraviolet (EUV) radiation drives the major ionization processes in the upper atmosphere. Its variability causes a related response in ionospheric observables. Especially of interest is the delayed response of electron density (Ne), integrated total electron content (TEC), and the density of major neutral and ionized species to the 27-d solar rotation period. But this solar signature is often influenced by underlying trends on shorter and longer time-scales. Therefore, this study examines the ionospheric response to a solar 27-d signature superposed with a long-term increase in solar EUV, showing that complex composition changes in the upper atmosphere influence the expected response significantly. Using high-resolution simulations of the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM), we compare two different 27-d solar rotation periods from the year 2014 with enhanced solar activity. This allows us to compare an almost ideal solar activity input with one that is superposed with an increase in solar activity. The main results show that the accumulation of ionized species O+ and O2+ in the lower ionosphere, especially up to the maximum density of ionized oxygen (O+) at about 230 km, is significantly affected by the long-term increase in solar activity.  Nevertheless, the 27-d solar rotation period dominates the ionization in both, ideal and complex model run for altitudes above 230 km. Thus, our results are in good agreement with preceding studies and extend the study of the delayed ionospheric response to more complex cases.

How to cite: Dühnen, H., Vaishnav, R., Schmölter, E., and Jacobi, C.: Solar variability and delayed ionospheric response: Insights from complex 27-day solar EUV signatures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1426, https://doi.org/10.5194/egusphere-egu24-1426, 2024.

X3.36
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EGU24-2966
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ECS
Coupling between thermospheric gravity waves and non-migrating tides simulated by the Whole Atmosphere Model
(withdrawn)
Garima Malhotra, Timothy Fuller-Rowell, Christopher J. Heale, Tzu-Wei Fang, Valery Yudin, Svetlana Karol, and Adam Marshall Kubaryk
X3.37
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EGU24-3589
Phillip Anderson

GDC is a six-satellite constellation, designed to investigate the dynamics of the coupling between the ionosphere and thermosphere. The mission will provide multipoint observations of both the energy inputs and the ionosphere-thermosphere system response with sufficient spatial and temporal resolution to finally unravel the physical processes underlying the observed system-level dynamical responses. A critical component of the measurement requirements are the characteristics of the thermal plasma. TPS is a multi-sensor instrument designed to measure the three components of the ion drift, the ion density and temperature, and the mass fractions of the major constituent ions. We present an overview of the instrument, the methods by which the measurements are made, and the science questions to be addressed.

How to cite: Anderson, P.: The Thermal Plasma Sensor (TPS) for the Geospace Dynamics Constellation (GDC) mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3589, https://doi.org/10.5194/egusphere-egu24-3589, 2024.

X3.38
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EGU24-3841
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ECS
Tamás Bozóki and Jaroslav Chum

Gravity waves (GWs) are an important class of atmospheric waves that can propagate from the troposphere up to the upper atmosphere, where they can contribute significantly to the dynamical changes in the ionosphere. The aim of the present contribution is to gain a deeper understanding of the coupling between the lower and the middle ionosphere via gravity waves by the concurrent analysis of narrowband VLF measurements (characterizing GWs in the E layer) carried out at the Tihany Geophysical Observatory (TGO), Hungary and the multi-point and multi-frequency continuous Doppler sounding system (characterizing GWs in the F layer) operated by the Institute of Atmospheric Physics, CAS in the Czech Republic. The signal from the German VLF transmitter (call sign: DHO, frequency: 23.4 kHz) detected at the TGO have been considered for the present study, since the Doppler system located in the western part of the Czech Republic is close to the midpoint of the DHO-TGO wave propagation path. The inferred gravity wave activities have also been compared with the lightning locations provided by the World Wide Lightning Location Network (WWLLN) in order to identify the possible source areas of the upward propagating gravity waves. 

The preliminary analysis was carried out for the summer months of 2021. From the narrowband VLF measurements, the day-to-day variation of the average GW activity for each night was determined using the Wavelet transform. In the case of the Doppler system, the estimated Doppler shifts and the spreadF proxy were used to characterize the nighttime GW activity. Our results show low correlation (~0.04) between GW activity inferred from the VLF and Doppler measurements. On the other hand, for both the VLF and Doppler measurements, we could identify certain areas where the large number of lightning strokes was associated with enhanced GW activity in the corresponding ionospheric measurement. However, the areas found for the two measurements do not overlap, which may indicate that the VLF measurement is sensitive to a different area where the Doppler system is located. This work has been supported by the PITHIA-NRF Trans-National Access (TNA) programme.

How to cite: Bozóki, T. and Chum, J.: Comparison of gravity waves detected in the lower ionosphere by narrowband VLF measurements and in the F layer by a continuous Doppler sounding system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3841, https://doi.org/10.5194/egusphere-egu24-3841, 2024.

X3.39
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EGU24-6177
Wenbin Wang, Dong Ling, Slava Merkin, Qian Wu, and Yongliang Zhang

During geomagnetic storms, a latitudinally narrow band of strong sunward plasma drifts occurs just equatorward of auroral electron precipitation in the afternoon to pre-midnight sector, which is termed subauroral polarization steams (SAPS). SAPS are produced when the downward Region-2 current is closed through the subauroral region of low ionospheric conductivity and a strong poleward electric field is established to ensure current continuity. SAPS are a manifestation of the strong coupling between the magnetosphere and the ionosphere and thermosphere system. In this study, we employ the high-resolution Multiscale Atmosphere-Geospace Environment (MAGE) model that is developed by the NASA DRIVE Science Center for Geospace Storms (CGS) to simulate the SAPS effects on the global thermosphere-ionosphere system during the March 17 2013 geomagnetic storm. We compare two MAGE model runs, one with SAPS in the entire simulation and the other with the SAPS drifts being turned off when the ionospheric electric fields are used to calculate ion frictional heating, neutral Joule heating, ion drag and plasma transport. By comparing the results from these two runs we quantify the effects of SAPS on the thermosphere and ionosphere system. Our results show that with SAPS ionospheric total electron content (TEC) and electron densities are enhanced in the afternoon sector at middle and high latitudes. This provides a strong source of ionization for the high-latitude convection pattern to transport the plasma into the polar cap to form the polar tongue of ionization (TOI) and patches. Therefore, SAPS facilitate the occurrence and strengthening of TOI. The MAGE simulations also show that the phase and speed of storm-time traveling atmospheric disturbances and neutral circulation are modulated by the SAPS, and the SAPS effects are thus transmitted globally to affect the behavior of the entire thermosphere and ionosphere system during the storm.

How to cite: Wang, W., Ling, D., Merkin, S., Wu, Q., and Zhang, Y.: The Thermosphere and Ionosphere System Responses to Subauroral Polarization Streams (SAPS) During the March, 17, 2013 Geomagnetic Storm, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6177, https://doi.org/10.5194/egusphere-egu24-6177, 2024.

X3.40
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EGU24-7983
Jan Rusz, Jaroslav Chum, and Jiří Baše

The amplitude of GWs increases with height due to the decrease in the density of the atmosphere, but at the same time the attenuation of the waves also increases with height due to the dissipation of energy through friction.

In this study, the propagation of GWs in the ionosphere is observed remotely, using multi-point, multi-frequency continuous HF Doppler sounding system situated in the western Czechia. The configuration of the system allows to determine not only the amplitude, but also the speed and direction of GWs propagation at different heights. An ionosonde located not far away from the Doppler sounding system is used to assign the reflection heights to individual measurements.

The amplitudes of medium-scale atmospheric gravity waves propagating in the ionosphere are measured and statistically processed to investigate the daily and annual variations, and their relation to the speed of the neutral winds and the measurement height. Results from periods of solar maximum and minimum are compared.

How to cite: Rusz, J., Chum, J., and Baše, J.: Amplitudes of medium scale gravity waves (GWs) in the ionosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7983, https://doi.org/10.5194/egusphere-egu24-7983, 2024.

X3.41
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EGU24-11018
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ECS
Xin Wang, Lei Cai, Anita Aikio, Heikki Vanhamäki, Ilkka Virtanen, Yongliang Zhang, Bingxian Luo, and Siqing Liu

Energetic particle precipitation is the major source of electron production that controls the ionospheric Pedersen and Hall conductances at high latitudes. Typically, the ionospheric conductances are estimated using either theoretical or empirical equations. The former method requires several ionospheric and thermospheric parameters as inputs. By contrast, empirical equations are simple, such as Robinson formulas and Galand formulas that have been widely used. In this study, we evaluate the empirical formulas of ionospheric conductances during four different types of auroral precipitation conditions based on 63 conjugate events observed by DMSP and EISCAT. The conductances calculated from the DMSP data with the empirical formulas are compared with those based on EISCAT measurements with the standard equations. The best correlation between these two is found when the empirical Robinson formulas are used in the presence of diffuse electron precipitation without ions. In the presence of ion precipitation, the correlation coefficients are smaller, but the correlation improves when the Galand formulas are used to estimate the contribution of ion precipitation to the conductances. For the condition of pure ion precipitation, the ionospheric conductances are increased up to 2-7 S for Pedersen and 2.5-10 S for Hall conductances. The increase is larger for a higher geomagnetic AE index. Overall, the empirical formulas applied to the DMSP particle spectra underestimate the ionospheric conductances.

How to cite: Wang, X., Cai, L., Aikio, A., Vanhamäki, H., Virtanen, I., Zhang, Y., Luo, B., and Liu, S.: Ionospheric conductance due to electron and ion precipitations based on the comparison between EISCAT and DMSP estimates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11018, https://doi.org/10.5194/egusphere-egu24-11018, 2024.

X3.42
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EGU24-12540
Lalit Mohan Joshi

High-rate Radio Occultation (RO) measurement using the COSMIC-2 constellation has enabled the observation of the transient changes in the ionosphere's three-dimensional (3D) structure.  This capability enables studying the changes to the 3D ionospheric structure during a geomagnetic storm. So far, the ionospheric storms (positive/negative ionospheric storms) that follow space weather events, have mostly been studied globally using two-dimensional (2D) TEC maps generated using ground-based networks. Ground-based networks also limit the measurements to only over the landmass and islands. High-rate 3D observation from COSMIC-2 can overcome these limitations of the ground-based networks. Such measurements provide 3D ionospheric variations over a large region lying within +/- 400 geographic latitude, with a spatiotemporal resolution significant enough to provide new insights.  This paper presents a 3D perspective of the ionospheric impact of the November 04, 2021, geomagnetic storm. In the present study, electron density has been binned with latitude, longitude, altitude, and time resolution of 60, 300, 25 km, and 2 hours, respectively. It must be noted that the present study excludes electron density variation below 225 km altitude where RO retrievals are not considered reliable. Some of the key observed features of the ionospheric storm under consideration are: (a) Large enhancement in the ionospheric plasma density due to the enhanced ‘fountain effect’ in the main phase is most significant in the topside ionosphere with a maximum variation observed above 450 km, (b) the most significant enhancement in the topside ionospheric plasma density (positive storm effect) was seen during the midnight period, irrespective of the longitude under consideration, (c) enhancement in the electron density also indicated some longitudinal dependence, and (d) most significant impact of the ionospheric storm was observed over the latitudinal belt lying beyond the poleward boundary of the EIA crests.  These and several other interesting observations will be presented. Results will also be discussed in light of the current understanding of ionospheric storms.

How to cite: Joshi, L. M.: Three-dimensional monitoring of Ionospheric storms using COSMIC-2 RO, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12540, https://doi.org/10.5194/egusphere-egu24-12540, 2024.

X3.43
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EGU24-13541
Catalin Negrea, Nikolay Zabotin, Marius Echim, and Mike Rietveld

Travelling Ionospheric Disturbances (TID) and the underlying Atmospheric Gravity Waves (AGW) have long been associated with cases of extreme geomagnetic activity. This is especially true for geomagnetic storms that have been linked to large scale TIDs (LSTID). However, in the case of mid-scale TIDs (MSTID), a clear correlation has yet to be shown with geomagnetic activity, except for isolated cases. Such a correlation has been long suspected and assumed, since the mechanism by which these waves are generated must be linked to particle precipitation and localized heating, which occurs to some extent at all levels of geomagnetic activity due to the solar wind - magnetosphere - ionosphere coupling.

Our study used 7 years of measurements from the Tromso dynasonde, specifically the electron density and ionospheric tilts height profiles. These are generally available at a 2-minute cadence and thus can be used to resolve the bulk of the gravity wave spectrum. The excellent height resolution of the data, as well as the directionality of the two ionospheric tilts allow us to quantify the TID activity using an estimator based on the power spectral density integral. This proxy for overall TID activity accounts for all waves from all sources: auroral, orographic, from tropospheric weather, etc. We then demonstrate the relative importance of auroral waves by showing that TIDs with a north-south propagating direction correlate very well with geomagnetic indices indicative of geomagnetic disturbances at high-latitude (the AE, Kp and Polar Cap Indices), while less so for the SYM-H index, which is more indicative of lower latitudes. Long-term correlations are discussed, with an emphasis on changes to the statistical distribution describing the correlation. Finally, a high-precision analysis was performed to pin-point the time-delay between geomagnetic and TID activity at Tromso. The results show a dominant population of TIDs characterized by a delay of 2-6 hours, with a secondary population with delays larger than 10 hours.

How to cite: Negrea, C., Zabotin, N., Echim, M., and Rietveld, M.: Statistical correlations between geomagnetic activity and high-latitude TIDs investigated with the Tromso Dynasode, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13541, https://doi.org/10.5194/egusphere-egu24-13541, 2024.

X3.44
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EGU24-13772
Aroh Barjatya, Robert Clayton, Shantanab Debchoudhury, Matthew Zettergren, Henry Valentine, Nathan Graves, Rachel Conway, Peter Ribbens, Joshua Milford, Kenneth Obenberger, Jeffrey Holmes, Jorge (Koki) Chau, Kristina Lynch, Sebastijan Mrak, and Terry Bullett

Solar eclipses present a unique opportunity to study the effects of a supersonic cooling shadow and its modulation of the structure and energetics of the ionosphere-thermosphere system. Atmospheric Perturbations around Eclipse Path (APEP) is an eclipse rocket campaign that launched 3 sounding rockets from White Sands Missile Range (WSMR) during the Oct 2023 annular eclipse and will launch 3 sounding rockets from the Wallops Flight Facility (WFF) during the April 2024 total solar eclipse. This campaign will be the first simultaneous multipoint spatio-temporal in-situ observations of electrodynamics and neutral dynamics associated with solar eclipses. For each eclipse, the first instrumented rocket will be launched ~35 minutes before peak local eclipse, second at peak local eclipse, third ~35 minutes after peak local eclipse. The launches are supported by ground-based observations from AFRL Digisondes for WSMR launch and by VIPIR Dynasonde and Millstone ISR for WFF launch. Ground based meteor radar observations of neutral winds are also performed for both eclipses. These observations will be used to constrain comprehensive modeling during data analysis. 

How to cite: Barjatya, A., Clayton, R., Debchoudhury, S., Zettergren, M., Valentine, H., Graves, N., Conway, R., Ribbens, P., Milford, J., Obenberger, K., Holmes, J., Chau, J. (., Lynch, K., Mrak, S., and Bullett, T.: APEP: Eclipse Sounding Rocket Campaign, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13772, https://doi.org/10.5194/egusphere-egu24-13772, 2024.

X3.45
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EGU24-14223
The Response of Geomagnetic Daily Variation and Ionospheric Currents to the Annular Solar Eclipse on 21 June 2020
(withdrawn after no-show)
Xiaocan Liu, Junjie Chen, Peng Han, and Jiuhou Lei
X3.46
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EGU24-17824
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ECS
Martin Cafolla, Sandra Chapman, Nick Watkins, Xing Meng, and Olga Verkhoglyadova

The variability of GPS positioning and timings impacts navigation, communication and other low-Earth orbit satellites and is affected by space weather. Ground GNSS observations of Total Electron Content (TEC) with 100 − 200 ground stations are used to compile global maps of TEC to monitor ionospheric response to space weather events. We consider Global Ionospheric Maps (GIMs) available at a 15-minute cadence and a spatial resolution of 1 × 1 degree longitide/latitude bins from the Jet Propulsion Laboratory (JPL). These are available over 2 solar cycles, providing an extensive data set covering both seasonal variation and quiet/active times. Our study uses feature extraction to identify regions of enhanced TEC that are contiguous in both space and time. For each map, we identify spatially contiguous High Density Regions (HDRs) as the region on the TEC map within which the level is exceeded by the top 1% of TEC values. We then apply a tracking algorithm over consecutive timestamps to obtain a set of labelled coherent space-time TEC HDRs. Extracting and following these HDRs over multiple years allows us to explore their statistical dependencies upon geomagnetic activity, latitude and season. Given a set of geomagnetic indices (Dst, Kp and/or F10.7) at some date-time, we can determine the locations of HDRs, how long they last and their size/brightness. Our analysis detects, labels and tracks HDR origin, path, areas, TEC intensities and duration. TEC estimation in the JPL data has higher accuracy over the continental US and Europe than in other areas. We consider how this non-uniform distribution of ground stations affect our results.

How to cite: Cafolla, M., Chapman, S., Watkins, N., Meng, X., and Verkhoglyadova, O.: Contiguous Space-time TEC Enhancements in JPL GIMs - Seasonal, Latitudinal and Activity dependence, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17824, https://doi.org/10.5194/egusphere-egu24-17824, 2024.

X3.47
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EGU24-18179
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ECS
Guilhem Chicot, Véronique Dehant, and Olivier De Viron

Recent studies have identified a quasi six-year oscillation (QSYO) spanning various Earth system parameters, including the length of day, polar motion, secular variation of the magnetic field, sea level, precipitation, terrestrial water storage, land ice, and winds. This oscillation is linked to fluid dynamics processes in the liquid outer core, yet the mechanism facilitating its transmission from the core to the broader Earth system remains unclear. One of the proposed scenario is the plausible role of the magnetic field as a conduit for transmitting the QSYO from the core to the climatic system

Leveraging data from atmospheric and magnetic models alongside observations from Global Navigation Satellite System (GNSS), our approach employs statistical analysis to explore the presence of the QSYO in the atmosphere. We specifically analyze various parameters in both the charged (e.g., Total Electron Content - TEC) and neutral (e.g., nebulosities) atmospheric layers. This study aims to establish the existence of the QSYO in the atmosphere and link its variations with those from core in the magnetic field. 

How to cite: Chicot, G., Dehant, V., and De Viron, O.: Correlation of Magnetic Field Dynamics and Atmosphere for the study of the quasi six-year oscillation from Earth's core, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18179, https://doi.org/10.5194/egusphere-egu24-18179, 2024.

X3.48
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EGU24-19953
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ECS
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Kateryna Lubyk, Mohammed Mainul Hoque, Claudia Stolle, and Andreas Wehrenpfennig

The ionospheric mid-latitude trough is a phenomenon which is characterized through an electron density depletion in the F-layer of the ionosphere at the sub-auroral zone. In this study, we identify and derive the mid-latitude ionospheric trough properties using high-resolution Global Ionospheric Maps (GIMs) from International GNSS Service (IGS), namely UQRG maps, which have a high temporal resolution of 15 minutes. Our study is based on an extensive database, which we obtained by detecting troughs between 1998 and 2022, including two complete solar cycles (23 and 24). We have analyzed essential factors that define the MIT, like the trough minimum position, width, depth, and occurrence probability. All these MIT parameters represent morphological characteristics of the midlatitude trough in dependence on the magnetic local time, geographic distribution, seasons, and solar and geomagnetic activity conditions, including solar wind plasma speed, interplanetary magnetic field components, and geomagnetic activity indices SYM-H and Hp30.

Since the MIT climatology and occurrence probability have not yet been included in widely used 3D electron density models like IRI, NeQuick, NEDM2020, etc., the discovered dependencies can be used to validate current MIT models and to develop new MIT models. The performance of the 3D electron density models might be enhanced by including an MIT model.

How to cite: Lubyk, K., Hoque, M. M., Stolle, C., and Wehrenpfennig, A.: Evaluation of the mid-latitude ionospheric trough using high-resolution IGS ionospheric maps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19953, https://doi.org/10.5194/egusphere-egu24-19953, 2024.

Open session on ionosphere and thermosphere