Displays

Tidal and planetary waves (PWs) in the mesosphere and lower thermosphere region could have significant impact on the upper thermosphere/ionosphere system through direct propagations, E region wind dynamo, and the change of residual circulations. We would like to show some results from BeiDou and COSMIC observations, as well as TIME-GCM simulations, to illustrate the lower/upper atmospheric couplings through different mechanisms. Generally, the spatial structures of the ionospheric responses to planetary waves agree with the ionospheric fountain effect, which indicates the important roles of equatorial wind dynamos in transmitting planetary wave signals to the ionosphere. The TIME-GCM simulations show that the zonal and meridional components of the planetary waves could result in evident vertical ion drift perturbations, while the net ionospheric effect is related to both their latitudinal structures and phases. The simulations also show that the change of tidal amplitudes and secondary PWs generated by PW-tide interaction are also important to the ionospheric variabilities. Besides, the couplings through PW-induced residual circulations are exhibited by both model simulations and TEC observations from BeiDou satellite system.

How to cite: Gu, S.-Y.: The upper atmospheric responses to tidal and planetary waves, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12350, https://doi.org/10.5194/egusphere-egu2020-12350, 2020.

It is now well accepted that the ionosphere and thermosphere are sensitive to forcing from the lower atmosphere (troposphere-stratosphere) owing mainly to the progress that have been made in the last decade in understanding the vertical coupling mechanisms connecting these two distinct atmospheric regions. In this regard, the studies linking the upper atmosphere (mesosphere-lower thermosphere-ionosphere) variability due to sudden stratospheric warming (SSW) events have been particularly important. The change of stratospheric 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 the SSWs events have been gained by studying the 2008/2009 SSW event, which occurred under extremely low solar flux conditions. Recently another SSW event in 2018/2019 occurred under similar low solar flux conditions. In this study we simulate both these SSW events using Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) and present the findings by comparing the ionospheric and thermospheric response to both these SSW events. The tidal characteristics of the semidiurnal solar and lunar tides and the thermospheric composition for both these SSW events are compared and the causes of varying responses are investigated.

How to cite: Siddiqui, T. A., Yamazaki, Y., and Stolle, C.: Comparing the ionospheric response to the 2008/2009 and 2018/2019 SSW events, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18642, https://doi.org/10.5194/egusphere-egu2020-18642, 2020.

Propagation of gravity waves (GWs) is studied in the troposphere and thermosphere/ionosphere. The investigation of GW propagation in the troposphere is based on measurements by large scale array of absolute microbarometers with high resolution that is located in the westernmost part of the Czech Republic. On the other hand, the propagation of GWs in the thermosphere/ionosphere is observed remotely, using multi-frequency and multi-point continuous HF Doppler sounding system operating in the western part of the Czech Republic. The reflection heights of sounding radio waves of different frequencies are determined from ionospheric sounder, located in Pruhonice in the vicinity of Prague. Propagation velocities and directions are in both cases calculated from time/phase delays between signals recorded at different locations. The investigation of propagation of GWs in the ionosphere is performed in three dimensions as the observation points (reflection points of radio signals) are separated both horizontally and vertically. It is shown that GWs in the ionosphere usually propagate with wave vectors directed obliquely downward, which means upward propagation of energy. In addition, seasonal and diurnal changes of propagation directions were found. Typical propagation velocities of GWs observed at ionospheric heights are much higher (~100 to 200 m/s) than those observed on the ground (several tens of m/s).        

How to cite: Chum, J., Podolska, K., Rusz, J., and Base, J.: Statistical investigation of gravity wave propagation in the Czech Republic and above , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2631, https://doi.org/10.5194/egusphere-egu2020-2631, 2020.

This paper studies the daytime medium scale traveling ionospheric disturbances (MSTIDs) in the mid- and low-latitude ionosphere for a period of nearly half a solar cycle (2014-2019) using SWARM observations. We specifically focus on daytime MSTIDs to rule out any contribution from nighttime plasma irregularities. Fluctuations in electron density are primarily used to identify the MSTIDs. These wave like structures are independently observed in both electron density and magnetic fluctuations, although they do not always show one to one correlation. In most cases, the structures are observed by both satellite ‘A’ and ‘C’, suggesting that their zonal extent is more than 140 km. The study makes an attempt to understand and explain the magnetic conjugate nature of the MSTIDs. To have a better understanding of the dynamics of the MSTIDs, ground based GPS-TEC and ionosonde data has been used on case to case basis, wherever available. Additionally, spatio-temporal statistics of MSTID distribution is presented.

How to cite: Nayak, C. and Buchert, S.: Characteristics of daytime medium scale traveling ionospheric disturbances (MSTIDs) as observed by SWARM, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8844, https://doi.org/10.5194/egusphere-egu2020-8844, 2020.

The lower altitude region of the ionosphere (60-150 km) is characterized by a strong coupling between the neutral atmosphere and ionospheric plasma. Due to the high ion-neutral collision rate the plasma at these altitudes is less constrained to follow the magnetic field lines compared to plasma at higher altitudes in the ionosphere. This both permits the development of the windshear mechanism responsible for the formation of sporadic E (Es) layers and affects the coupling between atmospheric gravity waves (AGWs) and the ionospheric plasma. 

AGWs transport energy from the lower atmosphere upward to higher altitudes. The wave amplitudes increase with altitude and eventually couple to the ionospheric plasma generating electron density perturbations or travelling ionospheric disturbances (TIDs). 

Es layers are high-density, narrow-altitude layers of enhanced electron density in the ionosphere’s E region. Contrary to what the name would suggest, Es occurs relatively frequently and its climatology has been characterised through ionosonde studies. Furthermore, the vertical structure of Es has been studied using sounding rockets. However, such measurements are very sparse and cannot be used to routine monitoring or for detecting the Es occurrence at a particular time and location. 

Monitoring AGW and Es layers is of great interest to many terrestrial applications, such as natural hazard warning systems, radio communications, and global navigation satellite system (GNSS) users. Recently, the coupling between Es layers and AGWs has also seen increased research attention. 

Spire operates a large constellation of 3U cubesats which carry a radio occultation (RO) GNSS receiver. For ionospheric studies, the satellites measure Total Electron Content (TEC) data in both zenith-looking and RO geometries using dual frequency observations. Furthermore, the high rate (50Hz) phase measurements that are generally used for neutral atmosphere RO can also be used to produce relative TEC profiles of the lower ionosphere with high vertical resolution (approximately 100m at E region altitudes). In this talk, we review recent results describing the coverage and quality of E region ionospheric measurements collected by Spire. Furthermore, we describe Spire's Es and AGW automated detection algorithm that is based on a Hilbert–Huang transform (HHT) of the relative TEC profiles and we compare our results with time coincident and co-located ionosonde data. We also look toward the future and describe how low cost cubesat constellations can be used for global monitoring of AGWs and Es layers. These first results also open the way to near real-time monitoring and classification of more general ionospheric anomalies

How to cite: Savastano, G., Nordström, K., Angling, M., Nguyen, V., Duly, T., Yuasa, T., and Masters, D.: Monitoring Perturbations in the Lower-Ionosphere Using GNSS Radio Occultation Observed from Spire's Cubesat Constellation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7390, https://doi.org/10.5194/egusphere-egu2020-7390, 2020.

The paper presents analysis and interpretation of observed perturbations of global wave dynamics in the Ionosphere-Thermosphere-Mesosphere (ITM) during the recent mid-winter Arctic Sudden Stratospheric Warming (SSW) events under solar minimum (2009, 2010, 2018, and 2019), transition to solar maximum (2012) and solar maximum (2013) conditions of the Solar Cycle 24. Employing the 116-level configuration of the thermosphere extension of Whole Atmosphere Community Climate Model (WACCMX-116L), constrained by the meteorological troposphere-stratosphere analyses of Goddard Earth Observing System, version 5 (GEOS-5) of Global Modeling and Data Assimilation Office, we study and characterize the striking amplifications of the solar thermal semidiurnal tide, as one of the main drivers of the ITM variability, after onsets of major and minor SSW events. The dominance and growth of the semidiurnal tide over the diurnal and terdiurnal modes in the lower thermosphere above ~100 km are typical features of the tidal dynamics during major SSW events of the Solar Cycle 24 as suggested by model predictions. The growth of the semidiurnal tidal mode during SSW events is also supported by observational analysis of diurnal cycles from temperature space-borne observations (SABER/TIMED). In the vertical domain of the meteor radar observations at the Southern extra-tropics and low latitudes the model and data revealed the systematic presence of the strong quasi two-day wave wind oscillations that prevail over the tidal winds between 80 and 100 km during mid-January SSW events. In the high and middle latitudes of the Northern Hemisphere model simulations are capable to reproduce the day-to-day variability of tidal and PW oscillations deduced from satellite temperature data. The self-consistent whole atmosphere predictions of global-scale components of neutral dynamics (prevailing winds, planetary waves and tides) become important factor to reproduce and forecast the perturbed state of the ITM as observed from the ground and the space during SSW events of the Solar Cycle 24. The SSW-driven global perturbations of tides can significantly change diurnal cycles of the plasma in the low-latitude and extra-tropical E-region of the ionosphere as will be briefly illustrated by day-day variations of observed and simulated total electron content and plasma drifts.

How to cite: Yudin, V., Goncharenko, L., Karol, S., and Harvey, L.: Perturbations of Global Wave Dynamics During Stratospheric Warming Events of the Solar Cycle 24, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6009, https://doi.org/10.5194/egusphere-egu2020-6009, 2020.

The hemispheric asymmetry of the ionospheric variation in the American sector (45°N~45°S, MLAT; 80°~60°W) is studied with total electron content (TEC) data during major sudden stratospheric warming events. The amplitude (A_M2) and relative strength (RS_M2) of the semi-diurnal lunar tidal component (M2) of TEC are analyzed. RS_M2 is the ratio between the energy of M2 and the energy of all the studied tidal components. The magnitudes of A_M2 and RS_M2 exhibit clear hemispheric and latitudinal variations. The A_M2 in the north of the magnetic equator tends to occur at lower magnetic latitudes than the A_M2 in the south of the magnetic equator. The RS_M2 exhibits similar features as the A_M2 but the difference is more distinct. We suggest that such hemispheric asymmetry of M2 parameters is related to the hemispheric asymmetry of the EIA and the latitudinal variation of the amplitude of the solar tidal components in winter.

How to cite: Zhang, D. and Liu, J.: Hemispheric asymmetry of the ionospheric variation during major sudden stratospheric warming events, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20247, https://doi.org/10.5194/egusphere-egu2020-20247, 2020.

Solar tides are the most predictably-occurring waves in the upper atmosphere. Although the dynamical theory can be dated back to Laplace in the 16th century, in the upper atmosphere tides  were rarely studied observationally until satellites and ground-based radars became common. To date, studies have mainly focused on low-order harmonics. Here, we combine mesospheric wind observations from three longitudinal sectors to investigate high-order harmonics. Results illustrate that the first six harmonics appear in early 2018, all of which are dominated by sum-synchronous components. Among these harmonics, the 6hr, 4.8hr, and 4hr components weaken at the sudden stratospheric warming (SSW) onset. The weakening could be explained in terms of variations in the background zonal wind.

How to cite: He, M., Forbes, J., Chau, J., Li, G., Wan, W., and Korotyshkin, D.: Variations of upper atmospheric high-order solar tidal harmonics during sudden stratospheric warming 2018, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4062, https://doi.org/10.5194/egusphere-egu2020-4062, 2020.

A sudden stratospheric warming (SSW) is an extreme wintertime meteorological phenomenon occurring mostly over the Arctic region. Studies have shown that an Arctic SSW can influence the whole atmosphere including the ionosphere. In September 2019, a rare SSW event occurred in the Antarctic region, following strong wave-1 planetary wave activity. The event provides an opportunity to investigate its broader impact on the upper atmosphere, which has been largely unexplored in previous studies. Ionospheric data from ESA's Swarm satellite constellation mission show prominent 6-day variations in the dayside low-latitude region during the SSW, including 20-70% variations in the equatorial zonal electric field, 20-40% variations in the electron density, and 5-10% variations in the top-side total electron content. These ionospheric variations have characteristics of a westward-propagating wave with zonal wavenumber 1, and can be attributed to forcing from the middle atmosphere by the Rossby normal mode “quasi-6-day wave” (Q6DW). Geopotential height measurements by the Microwave Limb Sounder aboard NASA's Aura satellite reveal a burst of global Q6DW activity in the mesosphere and lower thermosphere at this time, which is one of the strongest in the record. These results suggest that an Antarctic SSW can lead to ionospheric variability by altering middle atmosphere dynamics and propagation characteristics of large-scale waves from the middle atmosphere to the upper atmosphere.

How to cite: Yamazaki, Y., Matthias, V., Miyoshi, Y., Stolle, C., Siddiqui, T., Kervalishvili, G., Laštovička, J., Kozubek, M., Ward, W., Themens, D., Kristoffersen, S., and Alken, P.: Vertical Atmospheric Coupling during the September 2019 Antarctic Sudden Stratospheric Warming, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11224, https://doi.org/10.5194/egusphere-egu2020-11224, 2020.

The energy input from the solar wind and magnetosphere is thought to dominate the ionospheric response during geomagnetic storms. However, at the storm recovery phase, the role of forces from lower atmosphere could be as important as that from above. In this study, we focused on the geomagnetic storm happened on 6–11 September 2017. The ground-based total electron content (TEC) data as well as the F region in situ electron density measured by the Swarm satellites reveals that at low and equatorial latitudes the dayside ionosphere shows as prominent positive and negative responses at the Asian and American longitudinal sectors, respectively. The global distribution of thermospheric O/N2 ratio measured by global ultraviolet imager on board the TIMED satellite cannot well explain such longitudinally opposite response of the ionosphere. Comparison between the equatorial electrojet variations from stations at Huancayo in Peru and Davao in the Philippines suggests that the longitudinally opposite ionospheric response should be closely associated with the interplay of E region electrodynamics. By further applying nonmigrating tidal analysis to the ground‐based TEC data, we find that the diurnal tidal components, D0 and DW2, as well as the semidiurnal component SW1, are clearly enhanced over prestorm days and persist into the early recovery phase, indicating the possibility of lower atmospheric forcing contributing to the longitudinally opposite response of the ionosphere on 9–11 September 2017.

How to cite: Xiong, C., Luehr, H., and Yamazaki, Y.: An opposite response of the low-latitude ionosphere at Asian and American sectors during storm recovery phase: drivers from below and above, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5401, https://doi.org/10.5194/egusphere-egu2020-5401, 2020.

Beginning with 1959 that means over more than 60 years, field strength measurements of the broadcasting station, Allouis (Central France), have been carried out at Kühlungsborn (54° N, 12° E, Mecklenburg, Northern Germany. These so-called indirect phase-height measurements of low frequency radio waves (here with a frequency of 162 kHz) are used to examine the long-term evolution and trends of the mesosphere over Europe. The advantages of the method are the low costs and the simplicity of operation. The extended reanalyzed fifth release of standard-phase height (SPH) are presented.

The SPH-series are anti-correlated to the solar cycle as known because stronger photo-ionization is linked with higher number of electrons, which reduces the SPH. The anti-correlation between SPH and proxies of solar cycle are well established. Furthermore the statistical analysis of the SPH-series shows a significant overall trend in the order of hundred meters per decade induced by a shrinking stratosphere due to global warming. Strong intra-decadal variability is related to QBO like and ENSO like variability. The derived thickness temperature of the mesosphere decreased statistically significant over the period 1959-2019 after pre-whitening with summer means of solar sun spot numbers. The trend value is in the order of about -1 K/ decade if the stratopause trend is excluded. The amount of linear regression is weaker, -0.8 K/ decade for the period of 1963-1985 (2 SCs), but stronger, about -1.6 K/ decade during 1995-2016 (last 2 SCs).

How to cite: Peters, D. H. W. and Entzian, G.: Standard-Phase-height measurements over Europe during 60 years of measurements – Long-term variability and trends of the mesosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9551, https://doi.org/10.5194/egusphere-egu2020-9551, 2020.

The present work investigates the nighttime meridional wind (30º-50º magnetic latitude and 19-22 magnetic local time) in response to subauroral polarization streams (SAPS) that commence at different universal time (UT) by using Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) under geomagnetically disturbed conditions that are closely related to the southward interplanetary magnetic field (IMF) carried by the solar wind. The SAPS effects on the meridional winds show a remarkable UT variation, with larger magnitudes at 00 and 12 UT than at 06 and 18 UT. The strongest poleward wind emerges when SAPS commence at 06 UT, and the weakest poleward wind develops when SAPS occur at 00 UT. A diagnostic analysis of model results shows that the pressure gradient is more prominent for the developing of the poleward wind at 00 and 12 UT. Meanwhile, the effect of the ion drag is important in the modulation of the poleward wind velocity at 06 and 18 UT. This is caused by the misalignment of the geomagnetic and geographic coordinate systems, resulting to a large component of ion drag in geographically northward (southward) direction due to the SAPS channel orientation at 06 and 18 UT (00 and 12 UT). The Coriolis force effect induced by westward winds maximizes (minimizes) when SAPS commence at 12 UT (00 UT). The centrifugal force due to the accelerated westward winds shows similar UT variations as the Coriolis force, but with an opposite effect.

How to cite: Zhang, K., Wang, H., Wang, W., Liu, J., Zhang, S., and Sheng, C.: The nighttime poleward wind responses to SAPS simulated by TIEGCM: a universal time effect, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-381, https://doi.org/10.5194/egusphere-egu2020-381, 2020.

Abstract

Geomagnetic field variations in 2018 due to solar and lunar tides in the Brazilian sector were studied using data provided by magnetometers installed at São José dos Campos (23.21^oS, 0345.97^oW; Dip latitude 20.9^oS), Eusébio, Ceará (3.89° S, 38.46° W) and São Luís, Maranhão (2.53° S, 44.30° W). Variations associated with these tides were identified using the horizontal component of the geomagnetic field, H(nT). Least square fit method was employed in determining the monthly amplitudes and phases of the diurnal, semidiurnal and ter-diurnal solar tides. The monthly amplitudes and phases of the lunar tide were then calculated using the residual measurements (obtained after subtracting the solar tidal components from each day), converting the solar local time to lunar time and subjecting the residuals to harmonic analysis. The maximum solar tide amplitude recorded was 23.96nT(diurnal) in March, at Eusébio whereas the minimum amplitude was 0.45nT(terdiurnal) recorded in December at São José dos Campos. The lunar tide recorded a maximum amplitude of 4.33nT(semidiurnal) in February, at São Luís and a minimum amplitude of 0.13nT(diurnal) in August, at Eusébio.

Keywords: Solar tides, Lunar tides, Geomagnetic field, Magnetometer.

How to cite: Tsali-Brown, V. Y., Fagundes, P. R., Paulino, A. R., Pillat, V. G., and Bolzam, M. J. A.: Geomagnetic field variations due to Solar and Lunar tides in the Brazilian Sector, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1309, https://doi.org/10.5194/egusphere-egu2020-1309, 2020.

How to cite: Yin, F., Lühr, H., Park, J., and Wang, L.: Comprehensive Analysis of the Magnetic Signatures of Small‐Scale Traveling Ionospheric Disturbances, as Observed by Swarm, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7175, https://doi.org/10.5194/egusphere-egu2020-7175, 2020.

We study the correlation between wave activities in different layers of the atmosphere. The variability of the measured characteristic in the range of internal gravity wave periods is used as a proxy of wave activity. In the case of ground-based measurements, we consider temporal variations with periods less than ~ 6 hours; while in the case of satellite measurements we take into account spatial variations with periods less than ~ 1000 km. The wave activity is calculated as the standard deviation of variations in the indicated period range with averaging over one day. The aim of the study is to detect a correlation between day-to-day variations of wave activity in different layers of the atmosphere. Correlation coefficients are calculated for various intervals from one month to one year. Correlation analysis reveals the potential relationship between wave phenomena in the stratosphere, mesosphere and ionosphere. The study uses the following characteristics. The ionospheric characteristics are the peak electron density from the Irkutsk ionosonde (52.3 N, 104.3 E) and the total electron content from the Irkutsk GPS receiver. The characteristic of the mesosphere is the mesopause temperature from spectrometric measurements of the OH emission (834.0 nm, band (6-2)) near Irkutsk (51.8 N, 103.1 E, Tory). The stratospheric characteristic is the vertical gas velocity at 1 hPa from the ERA-Interim reanalysis (apps.ecmwf.int/datasets/data/).

This study was supported by the Grant of the Russian Science Foundation (Project N 18-17-00042). The observational results were obtained using the equipment of Center for Common Use «Angara» http: //ckp-rf.ru/ckp/3056/ within budgetary funding of Basic Research program II.12.

How to cite: Ratovsky, K., Medvedeva, I., Yasyukevich, A., Shpynev, B., and Khabituev, D.: Correlation between wave activities in different layers of the atmosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6863, https://doi.org/10.5194/egusphere-egu2020-6863, 2020.

The total electron content (TEC) data from Global Ionosphere Maps provide a global TEC map in the region between latitude 87.5°S to 87.5°N, and longitude 180°W to 180°E. The TEC data in geographic coordinates are first transformed into geomagnetic coordinates through Altitude-Adjusted Corrected Geomagnetic Model (AACGM). We then use 2-dimensional (longitudinal, 180°W-180°E and time, 10 days) Fourier transform (FT) of TEC variations along different geomagnetic latitude to obtain all wave modes in both UT (universal time) and LT (local time) frames for the period from November 18, 2002 to October 15, 2014. The summation of contributing wave modes at a given local time provides the longitudinal variation of the associated zonal waves. The phases of wave modes lead to a constructive or destructive interference of contributing zonal wave, which gives different structures at different local time. These local time structures include Weddell Sea Anomaly (WSA), Southern Atlantic Anomaly (SAA), and Four-peaked structure. The dependence of the peaked structures on latitudinal, seasonal, and solar activity is studied.

How to cite: Tsai, T.-C., Jhuang, H.-K., Lee, L.-C., and Ho, Y.-Y.: Observations of ionospheric TEC peaked structures from Global Ionosphere Maps, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12283, https://doi.org/10.5194/egusphere-egu2020-12283, 2020.

The tropical cyclone induced concentric gravity waves (CGWs) are capable of propagating upward from convective sources in the troposphere to the upper atmosphere and creating concentric traveling ionosphere disturbances (CTIDs). To examine the CGWs propagation, we implement tropical cyclone induced CGWs into the lower boundary of Global Ionosphere–Thermosphere Model with local-grid refinement (GITM-R). GITM-R is a three-dimensional non-hydrostatic general circulation model for the upper atmosphere with the local-grid refinement module to enhance the resolution at the location of interest. In this study, we simulate CGWs induced by typhoon Meranti in 2016. Information of the TC shape and moving trails is obtained from the TC best-track dataset and the gravity wave patterns are specified at the lower boundary of GITM-R (100 km altitude). The horizontal wavelength and phase speed of wave perturbation at the lower boundary are specified to be consistent with the TEC observations. The simulation results reveal a clear evolution of CTIDs, which shows reasonable agreement with the GPS-TEC observations. To further examine the dependence of the CTIDs on the wavelength and frequency of the gravity wave perturbation at the lower boundary, different waveforms have been tested as well. The magnitude of CTIDs has a negative correlation with the period, but a positive correlation with the wavelength when the horizontal phase velocities are sufficiently fast against the critical- level absorption.

How to cite: Zhao, Y., Lin, C.-Y., Deng, Y., Wang, J.-S., Zhang, S.-R., and Mao, T.: Tropical cyclone induced gravity wave perturbations in the upper atmosphere: GITM-R simulations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5541, https://doi.org/10.5194/egusphere-egu2020-5541, 2020.

Internal atmospheric waves interact with themselves and/or with the undisturbed atmospheric flow, creating very complicated dynamical system with long-range dependencies. We suspect that regional character of the atmosphere at tropospheric heights may be crucial for explanation of the three different dependencies of foF2 on F10.7cm. We employ multivariate statistic methods applied to daily observational data which were obtained using mid-latitude ionosondes for the investigation of these relationships.

We consider specific and characteristic atmospheric wave generation that correspond to particular climatology of each location “European”, “American” and “Far East”. Specific conditions of each region, involving meteorological phenomena of the location as spectrum of atmospheric wave generation and their propagation. We consider significant difference in low atmosphere climatology as a key explanation of the three classes of ionospheric response to the F10.7cm on long time-scales and suggest that climatology of the troposphere must be taken into account for modelling of the ionospheric response.

Our aim is also to demonstrate that conditional independence graph (CIG) models, representing a robust method of multivariet statistical analysis, are useful for finding a relation between the ionosphere and space weather. This method appears to be more appropriate than correlation analysis between foF2 and geomagnetic and solar indices, especially for longitudinal data for which the characteristics may change over time or time series is interrupted. This method seems more effective to us than correlation analysis or scale analysis.

The final results of our analysis by CIG show that the dependence time shifts were clearly identified, namely +0 day shift in all cases, and +3 / +4 / +5 day shift in the dependence on the solar cycle phase and geographical longitude. Here, we would like to point out that we have analyzed data from ionospheric stations in a rather short span of latitudes, all stations belong to midlatitudes (41.4° N – 54° N) and one would expect either practically same response/dependence of foF2 to F10.7 cm for longitudes and/or geomagnetic dependence as solar and geomagnetic forcing is considered as the most important. However, we have not identified any significant geomagnetically dependence with respect to selected stations and their geomagnetic location. Knowing that ionosphere is strongly coupled with lower-laying atmosphere, we come to the conclusion that climatology of the troposphere may come into play and be responsible for the difference in time-dependencies and time-lags in ionospheric response  to the external solar forcing.

How to cite: Podolská, K., Koucká Knížová, P., Chum, J., Kozubek, M., and Burešová, D.: Graphical models method - implementation to coupling processes in the atmosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4805, https://doi.org/10.5194/egusphere-egu2020-4805, 2020.

Abstract Ionosphere is an important error source of satellite navigation and a key component of space weather. With the rapid development of multiple Global Navigation Satellite System (GNSS) and other ionospheric research technologies, and the high precision and near real-time requirements for ionospheric products, it is necessary to carry out a research on multi-source data fusion, massive data processing and near-real-time solution of global ionosphere model (GIM); therefore, we modified the traditional ionospheric modeling technology and generate the GIM products (GIM/SHA). In view of the defect of ground-based GNSS data missing in the ocean regions, the method of adding virtual observation stations to the data missing regions in a large range was adopted, which not only enhanced the accuracy of the GIM in the ocean regions, but also avoided the weight determination among different data sources. In terms of near-real-time modeling, the multi-threaded parallel modeling strategy was adopted. Four GNSS (GPS, GLONASS, BEIDOU, Galileo) observation data, eight virtual observation stations and a server with a CPU frequency of 2.1 GHz and 16 threads were utilized. It took less than 30 minutes to construct the GIM by using parallel modeling strategy, which was 10.3 times faster than serial modeling strategy. The accuracy of the GIM/SHA was verified by using the ionospheric products of International GNSS Service (IGS) Ionosphere Associate Analysis Centers (IAACs) in the period of day of year (DOY) 200-365, 2019. Compared with the ionospheric products of CODE, ESA/ESOC, JPL, UPC, EMR, CAS and WHU, the vertical total electron content (VTEC) root mean squares (RMSs) were 1.09 TEC units (TECu), 1.51TECu, 2.32TECu, 1.88TECu, 2.24TECu, 1.25TECu and 1.38TECu, respectively. The result shows that the GIM/SHA have comparable accuracy with IGS ionospheric products. Satellite altimetry data was exploited to verify the accuracy of GIM/SHA in ocean regions, and it can be concluded that the accuracy of the GIM in ocean regions can be significantly reinforced by adding virtual observation stations in ocean regions. Multi-system and multi-frequency differential code bias (DCB) products (DCB/SHA) were simultaneously generated. Compared with IGS DCB products, the satellite DCB RMSs of DCB/SHA were 0.16ns for GPS, 0.08ns for GLONASS, 0.17ns for BEIDOU and 0.14ns for Galileo; the GNSS receiver DCB RMSs of DCB/SHA were 0.69ns for GPS, 1.06ns for GLONASS, 0.75 for BEIDOU and 1.03ns for Galileo. It can be proved that the accuracy of DCB/SHA are comparable to IGS DCB products.

Keywords Multi-GNSS; GIM; Virtual observation station; Near real-time; VTEC; DCB

How to cite: Jin, X., Song, S., Li, W., and Cheng, N.: Efficient global ionospheric modeling based on multi-source and massive observation data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16618, https://doi.org/10.5194/egusphere-egu2020-16618, 2020.

Through respectively adding June tides and December tides at the low boundary of GCITEM-IGGCAS model (Global Coupled Ionosphere-Thermosphere-Electrodynamics Model, Institute of Geology and Geophysics, Chinese Academy of Sciences), we simulate the influence of tides on the annual anomalies of the ionospheric electron density. The tides’ influence on the annual anomalies of the ionospheric electron density varies with latitude, altitude and solar activity level. Compared with the density driven by December tides, the June tides mainly increases the lower ionospheric electron density, and mainly decreases the electron density at higher ionosphere. In the low-latitude ionosphere, tide drives an additional equatorial ionization anomaly structure (EIA) at higher ionosphere in the relative difference of electron density, which suggests that tide affect the equatorial vertical E×B plasma drifts. Although the lower ionospheric annual anomalies driven by tides mainly increases with the increase of solar activity, the annual anomalies at higher ionosphere mainly decreases with solar activity.

How to cite: Ren, Z., Wan, W., Xiong, J., Liu, L., and Li, X.: Influence of tides on the ionospheric annual anomalies, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3044, https://doi.org/10.5194/egusphere-egu2020-3044, 2020.