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Vertical coupling in the Atmosphere-Ionosphere system

Earth’s atmosphere-ionosphere system is a stratified and vertically structured mix of gases that comprise different layers, i.e., the troposphere, stratosphere, mesosphere, and thermosphere, and its ionized part, the ionosphere. These layers are characterized by different combinations of dynamics, e.g., fluid-dynamic, chemical, and electrodynamical processes. The processes are coupled through various mechanisms, e.g., atmospheric circulations, disturbances, and various waves. The current session emphasizes the recent investigations of processes driving or reflecting vertical coupling within the atmosphere-ionosphere system in a broad range of spatial and temporal scales, such as atmospheric and ionospheric response to various waves (planetary waves, tides, gravity waves, etc.), transient phenomena (sudden stratospheric warming, seasonal transition), recurring patterns like QBO and ENSO, long-term trends in the middle and upper atmosphere and their drivers, and the relative importance of atmospheric and solar/magnetospheric forcing in the upper and middle atmosphere. This session invites contributions that discuss relevant methodologies, theory, modeling, experiment, and observations of different aspects of atmosphere-ionosphere coupling.

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Maosheng He, Yosuke Yamazaki, Larisa Goncharenko

Convener: Maosheng He | Co-conveners: Yosuke Yamazaki, Larisa Goncharenko
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Fri, 30 Apr, 13:30–15:00

Chairpersons: Maosheng He, Yosuke Yamazaki, Larisa Goncharenko

5-minute convener introduction

Huixin Liu et al.

We examine impacts of geomagnetic activity on CO2-driven trend in the Ionosphere and Thermosphere (IT) using the GAIA whole atmosphere model. The model reveals three salient features. (1) Geomagnetic activities usually weakens the CO2-driven trend at a fixed altitude. Among the IT parameters analyzed, the thermosphere mass density is the most robust indicator for CO2 cooling effect even with geomagnetic activity influences. (2) Geomagnetic activities can either strengthen or weaken the CO2-driven trend in hmF2 and NmF2, depending on local time and latitudes. This renders the widely used linear fitting methods invalid for removing geomagnetic effects from observations. (3) An interdependency exists between the efficiency of CO2 forcing and geomagnetic forcing, with the former enhances at lower geomagnetic activity level, while the latter enhances at higher CO2 concentration. This could imply that the CO2-driven trend would accelerate in periods of declining geomagnetic activity, while magnetic storms may have larger space weather impacts in the future with increasing CO2. These findings provide a preliminary model framework to understand interactions between the CO2 forcing from below and the geomagnetic forcing from above.

How to cite: Liu, H., Tao, C., and Jin, H.: Geomagnetic activity effects on CO2‐driven trend in the thermosphere and ionosphere:  ideal model experiments with GAIA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11128, https://doi.org/10.5194/egusphere-egu21-11128, 2021.

Jing Liu et al.

During Sudden Stratospheric Warming events, the ionosphere exhibits phase-shifted semi-diurnal perturbations, which are typically attributed to vertical coupling associated with the semi-diurnal lunar tide (M2). Our understanding of ionospheric responses to M2 is limited. This study focuses on fundamental vertical coupling processes associated with the latitudinal extent and hemispheric asymmetry of ionospheric M2 signatures, using total electron content data from the eastern Asian and American sectors. Our results illustrate that the asymmetry maximizes at around 15°N and 20°S magnetic latitudes. In the southern hemisphere, the M2-like signatures extend deep into midlatitude and, in the American sector, encounter the Weddell Sea Anomaly. The M2 amplitude is larger in the northern hemisphere and such asymmetry is more distinct in the eastern Asian sector. The hemispheric asymmetry of M2 signatures in the low latitude can be primarily explained by the trans-equatorial wind modulation of the equatorial plasma fountain. Other physical processes could also be relevant, including hemispheric asymmetry of the M2 below the F region, the ambient thermospheric composition and ionospheric plasma distribution, and the geomagnetic field configuration.

How to cite: Liu, J., Zhang, D., Goncharenko, L., Zhang, S.-R., He, M., Hao, Y., and Xiao, Z.: The hemispheric asymmetry of ionospheric lunitidal signatures during Sudden Stratospheric Warmings in the eastern Asian and American sectors, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7320, https://doi.org/10.5194/egusphere-egu21-7320, 2021.

Sumedha Gupta et al.

With low solar activity and unusual progression, Solar Cycle 24 lasted from December 2008 to December 2019 and is considered to be the weakest cycle in the last 100 years. During such quiet solar background conditions, the wave forcing from lower atmosphere will have a perceivable effect on the ionosphere. This study examines the ionospheric response to meteorological phenomenon of Sudden Stratospheric Warming (SSW) events during Solar Cycle 24 (Arctic winter 2008/09 to 2018/19). Ionospheric response to each of these identified warming periods is quantified by studying ground – based Global Positioning System (GPS) derived vertical Total Electron Content (VTEC) and its deviation from monthly median (ΔVTEC) for four longitudinal chains, selected from worldwide International GNSS service (IGS) stations. Each chain comprises of eight stations, chosen in such a way as to cover varied latitudes both in Northern and Southern Hemispheres. A strong latitude – dependent response of VTEC perturbations is observed after the peak stratospheric temperature anomaly (ΔTmax). The semidiurnal behaviour of VTEC, with morning increase and afternoon decrease, is mostly observed at near-equatorial stations. This vertical coupling between lower and upper atmosphere during SSW is influenced by prominent 13-14 days periodicities in VTEC observations, along with other periodicities of 7, 5, and 3 days. It is seen that the ionospheric response increases with increase in solar activity. Further, under similar ionizing conditions, quite similar ionospheric response is observed, irrespective of ΔTmax and type of SSW event being major or minor. However, under similar SSW strength (ΔTmax), no prominent pattern in ionospheric response is observed. The causative mechanism for the coupling processes in the atmosphere during these SSW events is discussed in detail.

How to cite: Gupta, S., Upadhayaya, A. K., and Siingh, D.: Ionospheric Variability: Response to Sudden Stratospheric Warming events during Solar Cycle 24, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3773, https://doi.org/10.5194/egusphere-egu21-3773, 2021.

Yaxian Li and Gang Chen

We present an analysis of the perturbations and wave characteristics in equatorial electrojet (EEJ) and equatorial zonal winds in the mesosphere and lower thermosphere region during three sudden stratospheric warming (SSW) events, based on the wind observations by two meteor radars in Indonesia and the geomagnetic field observations in India. During three SSWs, the shifting semidiurnal perturbations are consistently observed in the EEJ and accompanied with strong 2-day periodic perturbations simultaneously. The semidiurnal lunar (L2) tidal amplitudes in the EEJ and zonal winds show the prominent enhancements during the episodes of EEJ perturbations. The time-period spectra of the L2 tidal amplitudes in both the EEJ and zonal winds present the obvious quasi-2-day wave (QTDW) amplification with good agreement during these periods. Our results firstly reveal the important contributions of QTDW to EEJ perturbations during SSWs and the semidiurnal lunar tides modulated by QTDW serve as the main forcing agent therein

How to cite: Li, Y. and Chen, G.: Effect of Semidiurnal Lunar Tides Modulated by Quasi-2-Day Wave on Equatorial Electrojet during Three Sudden Stratospheric Warming events, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6985, https://doi.org/10.5194/egusphere-egu21-6985, 2021.

Hong Gao et al.

We studied O2 aurora based on the observations of O2 emission at 1.27 μm from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument during the nighttime over 18 years. The horizontal structure and vertical profile of O2 auroral volume emission rate is obtained after removing O2 nightglow contamination. The O2 auroral intensity varies between 0.14 and 5.97 kR, and the peak volume emission rate varies between 0.97 × 102 and 41.01 × 102 photons cm−3 s−1. The O2 auroral intensity and peak volume emission rate exponentially increases with increasing Kp index, whereas the peak height decreases with increasing Kp index. The O2 auroral intensity and peak volume emission rate under solar minimum condition are larger than those under solar maximum condition. The peak height under solar minimum condition is lower than that under solar maximum condition.

How to cite: Gao, H., Xu, J., and Zhu, Y.: The O2 aurora observed by the TIMED/SABER satellite, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-645, https://doi.org/10.5194/egusphere-egu21-645, 2021.

Guoying Jiang et al.

The reestimates of thermospheric winds from the Gravity field and steady-state Ocean Circulation Explorer (GOCE) accelerometer measurements were released in April 2019. In this study, we compared the new-released GOCE crosswind (cross-track wind) data with the horizontal winds measured by four Fabry-Perot interferometers (FPIs) located at low and middle latitudes. Our results show that during magnetically quiet periods the GOCE crosswind on the dusk side has typical seasonal variations with largest speed around December and lowest speed around June, which is consistent with the ground-FPI measurements. The correlation coefficients between the four stations and GOCE crosswind data all reach around 0.6. However, the magnitude of the GOCE crosswind is somehow larger than the FPIs wind, with average ratios between 1.37-1.69. During geomagnetically active periods, the GOCE and FPI derived winds have a lower agreement, with average ratios of 0.85 for the Asian station (XL) and about 2.15 for the other three American stations (PAR, Arecibo and CAR). The discrepancies of absolute wind values from the GOCE accelerometer and ground-based FPIs should be mainly due to the different measurement principles of the two techniques. Our results also suggested that the wind measurements from the XL FPI located at the Asian sector has the same quality with the FPIs at the American sector, although with lower time resolution.

How to cite: Jiang, G., Xiong, C., Stolle, C., Xu, J., Yuan, W., Makela, J. J., Harding, B. J., Kerr, R. B., March, G., and Siemes, C.: Comparison of thermospheric winds measured by GOCE and ground-based FPIs at low and middle latitudes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7082, https://doi.org/10.5194/egusphere-egu21-7082, 2021.

Zhipeng Ren et al.

Using GCITEM-IGGCAS model, we simulate the influence of the eastward propagating non-migrating diurnal tide with zonal wavenumber-3 (DE3) on nitric oxide (NO) infrared cooling rate. We find that the DE3 tide can drive a DE3 signal in lower thermospheric NO cooling rate, and the simulated altitudinal and seasonal variations are according with that of DE3 signal in equatorial lower thermospheric NO cooling rate observed by Oberheide et al. [2013], which is based on the TIMED/SABER observations during the solar minimum year 2008. This signal mainly shows an annual variation, which is stronger between June and September, and weaker near November. The maximum of the absolute signal, whose value is about 0.35*10-9 W/m3, occurs near the height of 130 km, but the relative signal mainly shows its peak with a value of 40% near the height of 100 km. Due to the difference of the driving mechanism, the distribution of NO signals in different latitudinal regions shows obvious difference. The middle- and low-latitude NO signal show smooth variation, while the high-latitude signal is discontinuous. The DE3 signal in NO cooling rate is mainly controlled by DE3 temperature tide and DE3 NO tide, meanwhile, the influences of DE3 neutral density tide on the DE3 signal can be ignored. The relative contributions of the DE3 NO tide and of the DE3 temperature tide vary with geographic latitude. The DE3 cooling rates in middle- and low- latitude and in high-latitude are respectively mainly driven by the DE3 temperature tide DE3 NO tide. DE3 tide may not only drive the DE3 signal, but also affect the lower thermospheric zonal mean NO cooling rate. The maximum of the absolute influence, whose value is about 0.12*10-9 W/m3, occurs above the height of 140 km, but the relative influence mainly shows its peak with a value of 10% near the height of 100 km.

How to cite: Ren, Z., Wan, W., Xiong, J., and Li, X.: A simulation of the influence of DE3 tide on nitric oxide infrared cooling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10514, https://doi.org/10.5194/egusphere-egu21-10514, 2021.

Tarique Adnan Siddiqui et al.

Owing to the progress that have been made in understanding the vertical coupling mechanisms in the last decade, it is now well established that the thermosphere-ionosphere system under quiet geomagnetic conditions is highly sensitive to lower atmospheric forcing.  In this regard, the studies linking the upper atmosphere (mesosphere-lower thermosphere-ionosphere) variability and sudden stratospheric warming (SSW) events have been particularly important. The changes to atmospheric circulation due to SSW events modulate the spectrum of vertically upward propagating atmospheric waves (gravity waves, tides, and planetary waves) resulting in numerous changes in the state of the upper atmosphere. Much of our understanding about the upper atmospheric variability associated due to SSWs events have been gained by studying the 2008/2009 Northern Hemisphere (NH) SSW event, which occurred under extremely quiet geomagnetic conditions. Recently, two major NH SSW events in the winter of 2018/2019 and 2020/2021 occurred under similarly quiet geomagnetic conditions. In this work, both these SSW events have been simulated using Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) and the low- and mid-latitude ionospheric response to both these SSW events will be presented.

How to cite: Siddiqui, T. A., Yamazaki, Y., and Stolle, C.: The ionospheric response to the 2019 and 2021 Northern Hemisphere SSWs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14705, https://doi.org/10.5194/egusphere-egu21-14705, 2021.

Yosuke Yamazaki and Yasunobu Miyoshi

A sudden stratospheric warming (SSW) is a large-scale meteorological phenomenon, which is most commonly observed in the Arctic region during winter months. In September 2019, a rare SSW occurred in the Antarctic region, providing a unique opportunity to study its impact on the middle and upper atmosphere. Geopotential height measurements by the Microwave Limb Sounder aboard NASA's Aura satellite reveal a burst of westward-propagating quasi-6-day wave (Q6DW) with zonal wavenumber 1 in the mesosphere and lower thermosphere following the SSW. At this time, ionospheric data from ESA's Swarm satellite constellation mission show prominent 6-day variations in the daytime equatorial electrojet intensity and low-latitude plasma densities. The whole atmosphere model GAIA reproduces salient features of the middle and upper atmosphere response to the SSW. GAIA results suggest that the observed ionospheric 6-day variations are not directly driven by the Q6DW but driven indirectly through tidal modulations by the Q6DW. An analysis of global total electron content data reveals signatures of secondary waves arising from the nonlinear interaction between the Q6DW and tides.

How to cite: Yamazaki, Y. and Miyoshi, Y.: Whole Atmosphere Coupling during the September 2019 Antarctic Sudden Stratospheric Warming, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8857, https://doi.org/10.5194/egusphere-egu21-8857, 2021.

Maosheng He et al.

Mesospheric winds collected by multiple meteor radars at mid-latitudes in the northern hemispheric are combined to investigate wave activities in June—October 2019. Dual-station approaches are developed and implemented to diagnose zonal wavenumber $m$ of spectral peaks.  In  September—October, diagnosed are quasi‐10‐ and 6‐day planetary waves (Q10DW and Q6DW, $m=$1), solar semi-diurnal tides with $m=$1, 2, 3 (SW1, SW2, and SW3), lunar semi-diurnal tide, and the upper and lower sidebands (USB and LSB, $m=$ 1 and 3) of Q10DW‐SW2 nonlinear interactions.  During June— September, diagnosed are Rossby-gravity modes ($m=$3 and 4 at periods $T=$ 2.1d and 1.7d), and their USBs and LSBs generated from interactions with diurnal, semi-diurnal, ter-diurnal, and quatra-diurnal migrating tides. These results demonstrate that the planetary wave-tide nonlinear interactions significantly increase the variety of waves in the mesosphere and lower thermosphere region (MLT).

How to cite: He, M., Chau, J. L., Forbes, J. M., Thorsen, D., Li, G., Siddiqui, T. A., Yamazaki, Y., Hocking, W. K., Jacobi, C., and Hoffmann, P.: Planetary wave-tide nonlinear interactions increase the variety of MLT waves in summer 2019, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-608, https://doi.org/10.5194/egusphere-egu21-608, 2021.

Anna Yasyukevich et al.

Based on the data of Total Electron Content (TEC) and OH rotational temperature, we analyze temporal and spatial features of the level of short-term variability (within the periods of up to several hours) at the ionosphere and the upper mesosphere. The study is carried out at three points located at mid-latitude, subauroral, and high-latitude regions during for more than 5 years period. The dynamics of variability, both in the ionosphere and at the mesopause, have the similar pattern with a clear seasonal variation. The maximum in the variability is registered in winter, and it exceeds up to 5-6 times the variability level during the summer period. This feature is observed regularly. The revealed dynamics does not correlate with changes the in geomagnetic and solar activities. The variability within considered periods is generally related to activity of Internal Gravity Waves in the upper atmosphere. We suggest that a source of the related seasonal variations in the variability may be the stratospheric high-velocity jet stream that develops in the subauroral regions during winter months. We propose a stratosphere disturbance index based on Era-5 Reanalysis data. The index is shown to have a maximum at subpolar regions and experience the similar regular seasonal variation with a maximum during winter months. We show a clear correlation between the mesosphere/ionosphere variability indices and the stratosphere disturbance index. The obtained results indicate a strong coupling between the short-period variability in the ionosphere, in the upper mesosphere, and in the subauroral stratosphere. The study is supported by the Russian Science Foundation Grant No. 20-77-00070.

How to cite: Yasyukevich, A., Sivtseva, V., Medvedeva, I., Chernigovskaya, M., Ammosov, P., and Gavrilyeva, G.: Stratospheric jet stream as a possible source for similar seasonal variations of the short-term variability in the ionosphere, upper mesosphere and subpolar stratosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7651, https://doi.org/10.5194/egusphere-egu21-7651, 2021.

Mani Sivakandan et al.

Northwest to southeast phase fronts with southwestward moving features are commonly observed in the nighttime midlatitude ionosphere during the solstice months at low solar activity. These features are identified as nighttime MSTIDs (medium scale traveling ionospheric disturbances). Initially, they were considered to be a manifestation of neutral atmospheric gravity waves. Later on, investigations showed that the nighttime MSTIDs are electrified in nature and mostly confined to the mid and low latitude ionosphere. Although the overall characteristics of the nighttime MSTIDs are mostly well understood, the causative mechanisms are not well known. Perkins instability mechanism was believed to be the cause of nighttime MSTIDs, however, the growth rate of the instability is too small to explain the perturbations observed. Recently, model simulations and observational studies suggest that coupling between sporadic-E layers and other type of E-region instabilities, and the F region may be relevant to explain the generation of the MSTIDs.

In the present study simultaneous observation from OI 630 nm all-sky airglow imager, GPS-TEC, ionosonde and Meteor radars, are used to investigate the role of E and F region coupling on the generation of MSTIDs .Nighttime MSTIDs observed on three nights (14 March 2020, 23 March 2020 and 28 May 2020) in the OI 630 nm airglow images over Kuehlungsborn (54°07'N; 11°46'E, 53.79N  mag latitude), Germany, are presented. Simultaneous detrended GPS-TEC measurements also shows presence of MSTIDs on these nights. In addition, simultaneous ionosonde observations over Juliusruh (54°37.7'N 13°22.5'E) show spread-F in the ionograms as well as sporadic-E layer occurrence.  Furthermore, we also investigate the MLT region wind variations during these nights. The role of Es-layers and the interplay between the winds and Es-layers role on the generation of the MSTIDs will be discussed in detail in this presentation.


How to cite: Sivakandan, M., Chau, J. L., Martinis, C., Otsuka, Y., Mielich, J., and Conte, F.: Investigation on the role of E-F region coupling processes on the generation of nighttime MSTIDs: Case studies over northern Germany, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12929, https://doi.org/10.5194/egusphere-egu21-12929, 2021.

Sahar Sobhkhiz et al.

Sporadic E (Es) is a transient phenomenon where thin layers of enhanced electron density appear in the ionospheric E region (90-120 km altitude). Es can influence radio propagation, and its global characteristics have been of great interest to radio communications and navigations. Atmospheric diurnal and semidiurnal tides cause horizontal wind shears at E-region heights by giving rise to ions and electrons' vertical motions. These shears will lead to the formation of Es layers. This research aims to study the role of atmospheric solar and lunar tides in Mid-latitude Es occurrence. For this purpose, radio occultation data from FORMASAT-3/COSMIC mission of 11 years (2007 to 2017), which provide complete global coverage, have been used. The results show both lunar and solar tidal signatures in Es occurrence. These tidal signatures are longitudinally dependent, which can result from non-migrating tides or modulation of migrating tidal signatures by zonally varying geomagnetic field.

How to cite: Sobhkhiz, S., Yamazaki, Y., and Arras, C.: Tidal Signature Detection in Midlatitude Sporadic E Occurrence Rate, Using FORMOSAT-3/COSMIC Radio Occultation Data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2400, https://doi.org/10.5194/egusphere-egu21-2400, 2021.

E. Liliana Macotela et al.

The seasonal variation of the daytime lower ionosphere, monitored using the propagation of Very Low Frequency (VLF) radio waves, shows an asymmetry when comparing the spring and autumn transitions. Considering the solar zenith angle variation, it can explain the spring transition but not the autumn one. The climatological variation exposes that the maximum of the VLF deviation is around the beginning of October. Thus, the deviation is called “the October effect”. This study aims to understand the possible atmospheric phenomena behind this effect. We use VLF signals transmitted from USA (NAA, f = 24 kHz), UK (GQD, f=19.6 kHz) and Iceland (NRK, f = 37.5 kHz) recorded in Northern Finland from 2011 to 2019. We compare our results with the Whole Atmosphere Community Climate Model with the thermosphere-ionosphere eXtension (WACCM-X) data. The October effect is separated into climatological earliest and latest effect according to WACCM-X climatological earliest and latest transitions from eastward to westward mean zonal winds

How to cite: Macotela, E. L., Pedatella, N., Marsh, D., Clilverd, M., Chau, J., Manninen, J., Banys, D., and Hansen, M.: Timing of the VLF October effect in relation to mesospheric wind dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10134, https://doi.org/10.5194/egusphere-egu21-10134, 2021.

Jack Wang et al.

An unusual sudden stratospheric warming (SSW) occurred in the Southern hemisphere in September 2019. Ground-based and satellite observations show the presence of a transient westward-propagating quasi-10 day planetary wave with zonal wavenumber one during the SSW. The planetary wave activity maximizes in the MLT region approximately 10 days after the SSW onset. Analysis indicates the quasi-10 day planetary wave is symmetric about the equator which is contrary to theory for such planetary waves. 

Observations from MLS and SABER provide a unique opportunity to study the global structure and evolution of the symmetric quasi-10 day wave with observations of both geopotential height and temperature during these unusual atmospheric conditions. The space-based measurements are combined with meteor radar wind measurements from Antarctica, providing a comprehensive view of the quasi-10 day wave activity in the southern hemisphere during this SSW. We will also present the results of our mesospheric and lower thermospheric analysis along with a preliminary analysis of the ionospheric response to these wave perturbations.

How to cite: Wang, J., Palo, S., Forbes, J., Marino, J., and Moffat-Griffin, T.: Burst of Unusual Quasi-10 day Wave During the 2019 Southern Sudden Stratospheric Warming, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-296, https://doi.org/10.5194/egusphere-egu21-296, 2020.

Larisa Goncharenko et al.

Limited observational evidence indicates that ionospheric changes caused by Arctic SSWs propagate to at least the middle latitudes in the Southern Hemisphere. However, it is not known if similar ionospheric anomalies are produced by Antarctic SSWs, mostly because Antarctic SSWs occur less often than the Arctic events. The sudden stratospheric warming of September 2019 has provided a perfect opportunity to investigate whether SSW are linked to upper atmospheric anomalies at middle latitudes of the opposite hemisphere. In this study we provide an overview of thermospheric and ionospheric anomalies observed in September 2019 at middle latitudes in the Northern Hemisphere. Our results indicate persistent and strong positive anomalies in total electron content and thermospheric O/N2 ratio observed in the western region of USA. Central and eastern regions of USA do not experience similar positive perturbations and show mostly moderate suppression of TEC reaching 20-40% of the baseline. Both positive and negative anomalies are observed over the central Europe. We discuss potential mechanisms that could be responsible for the observed features and suggest that regional differences in TEC response could be related to modulation of thermospheric winds by SSW and large declination angle over Western US.

How to cite: Goncharenko, L., Harvey, V. L., Greer, K., Zhang, S.-R., and Coster, A.: Impact of Antarctic Sudden Stratospheric Warming on Mid-Latitude Thermosphere and Ionosphere over USA and Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10289, https://doi.org/10.5194/egusphere-egu21-10289, 2021.

Astrid Maute et al.

The neutral wind dynamo plays an important role in generating low-latitude ionospheric variability and space weather. The characteristic equatorial ionization anomaly is generated by the daytime equatorial upward drift, which has imprinted on it the variation from upward propagating tides and waves. Observations and modeling studies have indicated large variability of the plasma drift on time scales from days to seasons associated with the wind dynamo at low and middle latitudes. The relationship of the ionospheric drift variability to the neutral wind variations is still not fully understood. The Ionospheric Connection explorer (ICON) mission is designed to focus on the low to middle latitude region and measures key parameters, such as the plasma drift and density and neutral temperatures and winds, to address the question of vertical coupling.

In this presentation, we will focus on the ICON observations and compare to Whole Atmosphere Community Climate Model-Extended (WACCM-X) simulations to examine the daytime low latitude ion drift and neutral wind variations. We investigate the day-to-day and longitudinal variation between concurrent ion drift and neutral wind variations over short time periods to quantify the contribution of the neutral wind in generating the ionospheric drift variations. Employing WACCM-X simulations, we investigate the importance of contributing factors, such as ionospheric conductivities, the geomagnetic main field, magnetosphere-ionosphere coupling, and the neutral wind, in generating the observed ionospheric drift variations. While we focus in this study on field line integrated ionospheric current density due to electric field/drift and neutral wind, we conclude by discussing our results in a more general context.

How to cite: Maute, A., Harding, B., Wu, J., Triplett, C., Heelis, R., Forbes, J. M., and Immel, T.: Examining and comparing observed and simulated daytime neutral wind and ionospheric drift variations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12567, https://doi.org/10.5194/egusphere-egu21-12567, 2021.

Steven Smith et al.

An extensive and bright mesospheric gravity wave event occurred over the El Leoncito Observatory, Argentina (31.8ºS, 69.3ºW) during the night of 17–18 March 2016. The wave structures were exhibited in the nightglow and were easily visible to naked eye observers, a phenomenon known as a Bright Night. Analysis of a combination of ground-based and space-based data sources indicated that the event was generated by a large thunderstorm complex located to the south-east of the observation site. The event was associated with very large values of wave momentum flux: 150–300 m2s-2, which is over an order of magnitude larger than typical. The routine seasonality of such thunderstorm systems suggests that they may contribute significantly to the role of upward coupling to the upper atmosphere and ionosphere. 

How to cite: Smith, S., Setvák, M., Yuri Beletsky, Y., Baumgardner, J., and Mendillo, M.: Mesospheric Gravity Wave Momentum Flux Generated by a Thunderstorm System, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10128, https://doi.org/10.5194/egusphere-egu21-10128, 2021.

Thomas Immel et al.

The electrodynamic influence of thermospheric winds is an effect thought to dominate the development of the daytime low-latitude ionosphere, through the generation of dynamo currents and associated vertical plasma drifts. Until recently, observations of the thermospheric and ionopsheric state variables have mainly been defined and compared on climatological time scales, due to their collection from separate observatories with disparate measurement capabilities.  These datasets are inadequate for investigation of the actual action of thermospheric drivers as they modify the ionospheric state, as the response clearly changes on 24-hour timescales, and shorter when viewed in the a constant-local-time frame of reference. New observatiions of thermospheric winds, uninterrupted over the 90-300 km altitude range, are now provided by the Ionospheric Connection Explorer along with simultaneous plasma velocity and density measurments. These observations are directly comparable to the wind measurements in crossings of the magnetic equator, where the winds are magnetically conjugate to the drift measurements. Investigation of the noon-sector drifts vs wind drivers is presented. We find that the local driver is clearly evident in the noon-time vertical plasma drifts under all conditions.


How to cite: Immel, T., Harding, B., Heelis, R., Maute, A., Forbes, J., England, S., Mende, S., Englert, C., Stoneback, R., Marr, K., Harlander, J., Makela, J., and Triplett, C.: The electrodynamic influence of thermospheric winds in the daytime ionosphere., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14252, https://doi.org/10.5194/egusphere-egu21-14252, 2021.

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