The term space weather indicates physical processes and phenomena in space caused by the radiation of energy mainly from the Sun. Solar and geomagnetic storms can cause disturbances in positioning, navigation and communication; coronal mass ejections (CME) can affect serious disturbances and in extreme cases damages or even destruction of modern infrastructure. The ionosphere and the thermosphere are parts of a physically coupled systems ranging from the Earth surface to the Sun including the magnetosphere and the lower atmosphere. Therefore, conducting detailed investigations on governing processes in the solar-terrestrial environment have key importance to understand the spatial and temporal variations of ionospheric and thermospheric key parameters such as the total electron content (TEC) and the plasma density of the ionosphere, as well as the thermospheric neutral density, which are influencing the orbits of Low-Earth orbiting (LEO) satellites. To address all these interrelations and impacts, the Global Geodetic Observing System (GGOS) Focus Area on Geodetic Space Weather Research was implemented into the structure of the International Association of Geodesy (IAG).

This session will address recent progress, current understanding, and future challenges of thermospheric and ionospheric research including the coupling processes. Special emphasise is laid on the modelling and forecasting of space weather time series, e.g. EUV-, X-ray radiation and CMEs, and their impact on VTEC and electron density. We encourage further contributions to the dynamo electric field, the variations of neutral and ion compositions on the bottom and top side of the ionosphere, atmospheric gravity waves and TIDs. Furthermore, we appreciate contributions on the wind dynamo, electrodynamics and disturbances, including plasma drift, equatorial spread F, plasma bubbles, and resultant scintillation.

Another main topic is global and regional high-resolution and high-precision modelling of VTEC and the electron density based on empirical, analytical or physical data assimilation approaches, which are designed for post-processing or (near) real-time purposes.

Co-organized by ST3
Convener: Ehsan ForootanECSECS | Co-conveners: Eren Erdogan, Michael Schmidt, Benedikt Soja, Chao XiongECSECS
| Attendance Thu, 07 May, 14:00–15:45 (CEST)

Files for download

Download all presentations (41MB)

Chat time: Thursday, 7 May 2020, 14:00–15:45

D1757 |
Mona Kosary, Saeed Farzaneh, Maike Schumacher, and Ehsan Forootan

Increasing the quality of ionosphere modeling is crucial and remains a challenge for many geodetic applications such as GNSS Precise Point Positioning (PPP) and navigation. Ionosphere models are the main tool to provide an estimation of Total Electron Content (TEC) to be corrected from GNSS career phase and pseudorange measurements. Skills of these models are however limited due to the simplifications in model equations and the imperfect knowledge of model parameters. In this study, an ionosphere reconstruction approach is presented, where global estimations of geodetic-based TEC measurements are combined with an ionospheric background model. This is achieved here through a novel simultaneous Calibration and Data Assimilation (C/DA) technique that works based on the sequential Ensemble Kalman Filter (EnKF). The C/DA method ingests the actual ionospheric measurements (derived from global GNSS measurements) into the IRI (International Reference Ionosphere) model. It also calibrates those parameters that control the F2 layer’s characteristics such as selected important CCIR (Comité Consultatif International des Radiocommunicationsand) URSI (International Union of Radio Science) coefficients.  The calibrated parameters derived from the C/DA are then replaced in the IRI to simulate TEC values in locations, where less GNSS ground-station infrastructure exists, as well as to enhance the prediction of TEC when the observations are not available or their usage is cautious due to low quality. Our numerical assessments indicate the advantage of the C/DA to improve the IRI’s performance. Values of the TEC-Root Mean Square of Error (RMSE) are found to be decreased by up to 30% globally, compared to the original IRI simulations. The importance of the new TEC estimations is demonstrated for PPP applications, whose results show improvements in navigation applications.

Keywords: Ionosphere, Calibration and Data Assimilation (C/DA), IRI, Total Electron Content (TEC), Precise Point Positioning (PPP), GNSS

How to cite: Kosary, M., Farzaneh, S., Schumacher, M., and Forootan, E.: Improving Total Electron Content (TEC) Models for Geodetic Applications, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-284, https://doi.org/10.5194/egusphere-egu2020-284, 2020.

D1758 |
Matthew Angling, Francois-Xavier Bocquet, German Olivares-Pulido, Sanita Vetra-Carvalho, Karl Nordstrom, Stacey Melville, and Giorgio Savastano

The ionosphere can affect a wide range of radio frequency (RF) systems operating below 2 GHz. One option for mitigating these effects is to produce assimilative models of the ionospheric density from which products can be derived for specific systems. Such models aim to optimally combine a background model of the ionospheric state with measurements of the ionosphere. This approach is analogous to the use of numerical weather prediction in the meteorological community, and has been evolving for ionospheric use for the last 10 to 15 years.

Published research has demonstrated the utility of this approach. However, obstacles to providing effective data products remain due to the sparseness of ionospheric data over large parts of the world and the timeliness with which data are available. Spire is working to overcome these issues through the use of its large constellation of satellites that can measure Total Electron Content (TEC) data in both zenith looking and radio occultation (RO) geometries and its large ground station network that will allow low data latency.

Spire data will be combined with an innovative data assimilation model (the Spire TEC Environment Assimilation Model, STEAM) to provide accurate and actionable ionospheric products. Data assimilation is required to overcome the limitations and assumptions of the traditional Abel Transform analysis of RO data (i.e., spherical symmetry; transmitter and receiver in free space and the same plane) and to effectively combine RO data, topside data, ground-based GNSS data, and other sources of ionospheric information (i.e., ionosondes).

STEAM uses a 4D Local ensemble transform Kalman Filter (LETKF). As with other ensemble methods, the LETKF uses an ensemble of models to approximate the background error covariance matrix. However, the LETKF provides a more efficient way to solve the ensemble equations. Furthermore, 4D operation permits the use of data with varying latency. Localisation means that grid points are only modified by data within a local volume; this restricts spurious long-range spatial correlations and means that the ensemble only has to span the space locally. The LETKF transforms the problem into ensemble space which makes each grid point independent, resulting in an algorithm that is easily parallelised.

This paper will describe the data collection and processing chain, the data assimilation model, and plans for the ongoing development of the combined system. 

How to cite: Angling, M., Bocquet, F.-X., Olivares-Pulido, G., Vetra-Carvalho, S., Nordstrom, K., Melville, S., and Savastano, G.: The Spire TEC Environment Assimilation Model (STEAM), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19447, https://doi.org/10.5194/egusphere-egu2020-19447, 2020.

D1759 |
Teresa Barata, Anna Morozova, and Tatiana Barlyaeva

The total ionospheric content (TEC) over the midlatitudinal area of Iberian Peninsula was studied using data from two locations on the west and east coasts of the peninsula. The data are obtained both by the GNSS receivers and an ionosonde. The principal component analysis applied to the TEC data allowed us to extract two main modes.

The variations of these modes as well as the original TEC data were studied in relation to geomagnetic disturbances observed in March, June, October, and December of 2015. Seven of eight analyzed geomagnetic events were associated with positive-negative ionospheric storms (seen both in TEC daily cycle amplitude and in Mode 1).

Four out of eight analyzed geomagnetic events were associated with variations of Mode 2 that can be described as the appearance of the second daily peak on the 1st day of the storm and a deep in TEC variations on the 2nd day.

Besides, we analyzed the effects of solar flares and overall variations of the solar UV and XR fluxes on the TEC variations during those months. Since a partial solar eclipse was observed in March 2015, the TEC variations during this event were also studied. Only the amplitude of the daily TEC cycle (Mode 1) was found to respond to these types of events.

How to cite: Barata, T., Morozova, A., and Barlyaeva, T.: Variations of TEC over Iberian Peninsula in 2015: effects of geomagnetic storms, solar flares, and solar eclipse, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3450, https://doi.org/10.5194/egusphere-egu2020-3450, 2020.

D1760 |
Gabriel Jerez, Fabricio Prol, Daniele Alves, João Monico, and Manuel Hernández-Pajares

The development of GNSS (Global Navigation Satellite System) and LEO (Low Earth Orbiting) satellites missions enhanced new possibilities of the terrestrial atmosphere probing. The Radio Occultation (RO) technique can be used to retrieve profiles from the neutral and the ionized atmosphere. An important advantage of using RO data is the spatial distribution, which enables global coverage. The signal transmitted by GNSS satellites and tracked by receivers embedded at the LEO satellites is influenced by the atmosphere which causes signal refraction. Due to the signal and atmospheric interaction, instead of a straight line, the signal propagates as a curved line in the path between the transmitter and receiver. The satellites geometry allows the retrieval of atmospheric refractive index, which carries several characteristics from its composition, such as pressure and temperature of the neutral atmosphere, and electron density of the ionosphere. In 1995 GPS/MET (Global Positioning System/Meteorology) experiment was launched to prove the RO concept and, since then, several LEO missions with GNSS receiver embedded were developed, such as CHAMP (Challenging Mini-satellite Payload) (2001-2008), SAC-C (Satélite de Aplicaciones Cientificas-C) (2001-2013) and COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) (2006-present). COSMIC is one of the RO missions with the greatest amount of atmospheric data available, mainly taking into account ionospheric information. In the RO technique, in general, the Abel retrieval is used to retrieve the refractive index. The Abel retrieval assumes a spherical symmetry of the atmosphere. When considering the electron density profiles, the main issue is related to regions with large horizontal gradients, where the spherical assumption presents the biggest degradation. In order to improve the ionospheric horizontal gradient used to retrieve electron density profiles, many researches have performed experiments using data from different sources. In this paper, we aimed to assess the electron density profiles over the Brazilian area (equatorial region), characterized by intense ionospheric variability, considering RO data and Global Ionospheric Maps (GIM). The data used is from COSMIC mission, in a period close to the last solar cycle peak (2013-2014). Ionosonde data were used as reference values to assess the RO with GIM aided data. Total Electron Content (TEC) data from GIM were used to estimate the variability of ionosphere between the ionosonde position and the profile locations. This research builds on a preliminary investigation related to the assessment of RO ionospheric profiles over a region under intense ionospheric variability, such as the Brazilian territory. Future works may take into consideration the use of other ionospheric information such as regional ionospheric maps, with higher resolution, and ionospheric tomography.

How to cite: Jerez, G., Prol, F., Alves, D., Monico, J., and Hernández-Pajares, M.: Assessment of electron density profiles over the Brazilian region using radio occultation data aided by global ionospheric maps , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-325, https://doi.org/10.5194/egusphere-egu2020-325, 2020.

D1761 |
Wenwen Li, Min Li, Qile Zhao, Chuang Shi, and Rongxin Fang

Electron density profiles (EDP) obtained by GNSS radio occultation (RO) technique can improve the primary ionospheric parameters. However, current studies mainly focused on GNSS RO measurements observed by low Earth orbit satellites, which can only estimate EDP at low altitudes typically below 1000 km. We investigated the GPS RO measurements recorded on the geostationary earth orbit (GEO) satellite TJS-2 (telecommunication technology test satellite II). To improve EDP derivation precision, the total electron content derived from TJS-2 single-frequency excess phase is refined by a moving average filter, which can smooth high-frequency errors and indicate higher precision over the single-difference technique. By comparison with the ground-based digisonde, the IRI 2016 model and the Constellation Observing System for Meteorology, Ionosphere, and Climate satellite (COSMIC) EDPs, the TJS-2 ionospheric EDPs show good agreement with correlation coefficients exceeding 0.8. The TJS-2 average NmF2 differences compared to digisondes and COSMIC results are 12.9% and 1.4%, respectively, while the hmF2 differences are 1.65 km and 1.76 km, respectively. With a GEO satellite such as TJS-2, the side lobe GPS RO signals can also be received, and they are employed to estimate electron densities up to several thousand kilometers in height for the first time in this contribution. Our results also reveal that GEO-based RO signals can estimate EDPs at specific locations with daily repeatability, which makes it a very suitable technique for routinely monitoring EDP variations

How to cite: Li, W., Li, M., Zhao, Q., Shi, C., and Fang, R.: Extraction of electron density profiles with geostationary satellite-based GPS side lobe occultation signals, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1569, https://doi.org/10.5194/egusphere-egu2020-1569, 2020.

D1762 |
Guanyi Ma, Qi Li, Takashi Maruyama, Jinghua Li, Qingtao Wan, Jiangtao Fan, Xiaolan Wang, and Jie Zhang

Ionospheric irregularities disrupt the propagation of radio waves in the frequency range below a few GHz, a band used by navigation and communication systems such as Global Navigation Satellite System (GNSS). Detailed understanding of the irregularity characteristics is helpful to estimate potential degradation of the performance of radio systems. We develop an algorithm to obtain high spatial resolution vertical total electron content (VTEC) and propose a spatial fluctuation of total electron content (TEC), SFT parameter, to analyze ionospheric irregularities by using the world’s densest GNSS Earth Observation Network (GEONET) of Japan. The data used in this study are carrier phase of the dual frequency GNSS signals from more than 1300 GNSS receivers of GEONET. VTEC is derived by assuming that it is identical in a 0.1°×0.1° grid, and removing a quantity representing inter-frequency hardware bias mixed with integer ambiguity. SFT is defined as the spatial dispersion of TEC within a specific area at a given time. The size of the specific area for SFT calculation is chosen as 0.8°× 0.8° in longitude and latitude, which corresponds to approximately 77 km×95 km at 400 km height at 35°N of Japan. An SFT map is generated by sliding window to show the spatial variation of ionospheric irregularities in two dimensions. The map can be used to obtain the size, shape, orientation and intensity distribution of the irregularity structures. Case studies are carried out for three strong irregularity events on 12 February 2000, 20 March 2001 and 10 November 2004. The irregularities are found to be anisotropic branching structures, which elongate in north-south direction when first seen at lower latitudes. The structures can move and deviate from their previous orientations, and eventually drift perpendicular to their orientations. Such analyses of SFT maps with GEONET observation successfully provide a new perspective of irregularity morphology and evolution.

How to cite: Ma, G., Li, Q., Maruyama, T., Li, J., Wan, Q., Fan, J., Wang, X., and Zhang, J.: Ionospheric irregularities detected by GEONET, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2837, https://doi.org/10.5194/egusphere-egu2020-2837, 2020.

D1763 |
Ali Mohandesi, David Knudsen, and Susan Skone

Ionospheric irregularities are a major error source in GNSS positioning and navigation as they affect trans-ionospheric signal propagation. They cause random, rapid fluctuations in the intensity and phase of the received signal, referred to as ionospheric scintillations. From a global point of view, GNSS signal scintillations are more severe and frequent in the equatorial region and during post-sunset hours. Characterizing irregularities that interfere most with navigation signals requires high-temporal resolution of measurements. In this work we utilize high-rate upward-looking measurements accomplished by the GAP RO receiver on CASSIOPE (Swarm Echo) satellite to study GPS signal scintillations and irregularities associated with them. This was done by reorienting CASSIOPE by approximately 90 degrees for short periods during November and December, 2019 while it passed through low-latitude region during post-sunset hours local time. High-rate GAP RO measurements provide a unique opportunity to investigate small-scale irregularities that are responsible for signal scintillations.

How to cite: Mohandesi, A., Knudsen, D., and Skone, S.: Characterization of Equatorial Low Latitude Ionospheric Scintillation of GPS Signals: An E-POP Experiment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10112, https://doi.org/10.5194/egusphere-egu2020-10112, 2020.

D1764 |
Armin Corbin, Kristin Vielberg, Michael Schmidt, and Jürgen Kusche

The neutral density in the thermosphere is directly related to the atmospheric drag acceleration acting on satellites. In fact, the atmospheric drag acceleration, is the largest non-gravitational perturbation for satellites below 1000 km that has to be considered for precise orbit determination. There are several global empirical and physical models providing the neutral density in the thermosphere. However, there are significant differences between the modeled neutral densities and densities observed via accelerometers. More precise thermospheric density models are required for improving drag modeling as well as orbit determination. We study the coupling between ionosphere and thermosphere based on observations and model outputs of the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM). At first, we analyse the model’s representation of the coupling using electron and neutral densities. In comparison, we study the coupling based on observations, i.e., accelerometer-derived neutral densities and electron densities from a 4D electron density model based on GNSS and satellite altimetry data as well as radio occultation measurements. We expect that increased electron densities can be related to increased neutral densities. This is indicated for example by a correlation of approximately 55% between the neutral densities and the electron densities computed by the TIE-GCM. Finally, we investigate whether neutral density simulations fit better to in-situ densities from accelerometry when electron densities are assimilated.

How to cite: Corbin, A., Vielberg, K., Schmidt, M., and Kusche, J.: Impact of electron density values from space-geodetic observation techniques on thermospheric density models, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7800, https://doi.org/10.5194/egusphere-egu2020-7800, 2020.

D1765 |
Lea Zeitler, Michael Schmidt, Mathis Bloßfeld, and Sergei Rudenko

The motion of a satellite depends on gravitational and non-gravitational accelerations. A major problem in precise orbit determination (POD) of low-Earth orbiting (LEO) satellites is modelling the thermospheric drag. It is the largest non-gravitational acceleration acting on satellites with altitudes lower than 1000 km and decelerates them. In case of the Swarm satellites with an altitude of around 460 km not considering the drag within a POD would cause an error of around 3 meters per revolution in the along-track direction.

In this study, we present results of DGFI-TUM in the context of the project TIPOD (Development of High-Precision Thermosphere Models for Improving Precise Orbit Determination of Low-Earth-Orbiting Satellites) funded by DFG in the frame of the SPP 1788 ‘Dynamic Earth’. One aim of this project is the computation of scaling factors for the thermospheric density from different satellite observation techniques, such as SLR, DORIS, GNSS or accelerometry. For a joint estimation of thermospheric model parameters the spatial, temporal and spectral content of the different scaling factors have to be analysed and interpreted. For example, accelerometer measurements along the satellite orbit provide scaling factors as point values. In this study we derive scaling factors from SLR measurements which could be interpreted as quasi-point values.

For the POD of LEO satellites, DGFI-TUM’s software package DOGS (DGFI-TUM Orbit and Geodetic parameter estimation Software) is used. It is characterized by the ability to process observations of different space geodetic techniques and to combine their linear parameter estimation systems within a joint Gauss-Markov model.

Here, we estimate scaling factors for the thermospheric density with a time resolution much higher than in our previous studies. Therefore, we use information of short passages from selected spherical satellites above SLR ground stations. Different temporal resolutions for the scaling factors varying from 6 hours down to 5 minutes will be tested and discussed in terms of reliability.

How to cite: Zeitler, L., Schmidt, M., Bloßfeld, M., and Rudenko, S.: Calculation of temporally high-resolution scaling factors for the thermospheric density from SLR observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15238, https://doi.org/10.5194/egusphere-egu2020-15238, 2020.

D1766 |
Yue Deng

We present a systematical study crossing both data analysis and model simulation to improve the specification of the energy and momentum inputs into the ionosphere-thermosphere (IT) system, especially at meso-scale, and the system response. Our results are organized in two parts, meso-scale forcing from above and from below. First, the meso-scale forcing from magnetosphere including flow burst, electric field variability, meso-scale particle precipitation and field-aligned current (FAC) has been analyzed using both satellite and ground-based measurements. The forcing distributions are then implemented in the Global Ionosphere-Thermosphere Model (GITM) to assess the relative contributions of meso-scale forcing to the ionosphere-thermosphere (I-T) system. Secondly, the acoustic gravity waves (AGWs) trigged by the geographic events, such as hurricane and volcano, propagate from lower atmosphere to I-T and cause disturbances observable for the Global Navigation Satellite Systems (GNSS). GITM with local-grid refinement (GITM-R) has been utilized to simulate ionospheric total electron content (TEC) variations induced by those events and compared with GNSS observations. These high-resolution simulations will strongly enhance our understanding and capability to specify the meso-scale forcing for the I-T system.

How to cite: Deng, Y.: What is the influence of meso-scale forcing on the ionosphere-thermosphere system?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12553, https://doi.org/10.5194/egusphere-egu2020-12553, 2020.

D1767 |
Lucas Schreiter, Claudia Stolle, Daniel Arnold, and Adrian Jäggi

Slant Total Electron Content (sTEC) measurements can be obtained by dual-frequency GPS
onboard Low Earth Orbiting (LEO) satellites. Within the last few years, a fleet of LEO Satellites at
altitudes ranging from 450 km (Swarm A/C) to 815 km (Sentinel 3) became operational. With
Swarm B, the recently launched GRACE-FO, and the Sentinel 1 and 2 satellites orbiting at
intermediate altitudes, we gain insight into the altitude dependent profile of the topside ionosphere
and plasmasphere.
We make use of this constellation to estimate a global three dimensional model of the electron
density distribution and will also carefully asses the impact of different profile functions, geometry-
free phase center variation maps and the P1-P2 receiver biases. Since the absolute value of the P1-
P2 biases are generally unknown, we focus on a consistent estimation for the whole LEO
We will present first results for selected months in 2019 and investigate the day to day variability of
the topside ionosphere and plasmasphere. We also intend to make use of COSMIC-2 data to
improve local time coverage in equatorial regions.

How to cite: Schreiter, L., Stolle, C., Arnold, D., and Jäggi, A.: Altitude dependent empirical modeling of the topside ionosphere and plasmasphere using GPS- TEC from Swarm, GRACE-FO and the Sentinel satellites., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4809, https://doi.org/10.5194/egusphere-egu2020-4809, 2020.

D1768 |
Fabricio Prol and Mainul Hoque

The plasmasphere is a region of continuous study due to some open questions related to the plasmaspheric internal dynamics, boundaries, and coupling processes with the magnetosphere and ionosphere, in particular during space weather events. Given such interests, the results of a new tomographic method to estimate the plasmaspheric electron density will be presented. The tomographic reconstruction is applied using measurements of Total Electron Content (TEC) from the Global Positioning System (GPS) receivers aboard the Constellation Observing System for Meteorology, Ionosphere, and Climate / Formosa Satellite Mission 3 (COSMIC/FORMOSAT-3). Despite relevant challenges imposed by the orbital geometry to obtain stable electron density reconstructions of a large area such as the plasmasphere, the developed approach was capable of representing the natural variability of the plasma ambient in terms of geographic/geomagnetic latitude, altitude, solar activity, season, and local time. The quality assessment was carried out using two years of in-situ electron density measurements from spacecraft deployed by the Defense Meteorological Satellite Program (DMSP). Our investigation revealed that improvements over 20% can be achieved for electron density specification by TEC data assimilation into background ionization.

How to cite: Prol, F. and Hoque, M.: Plasmaspheric electron density estimation based on COMISC/FORMOSAT-3 data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7526, https://doi.org/10.5194/egusphere-egu2020-7526, 2020.

D1769 |
Chao-Yen Chen and Jann-Yenq Liu

This paper investigates the plasmapause positions in the ionosphere by measurement of the whistler count probed by DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite in the daytime at 1030 LT (local time) and the nighttime at 2230 LT during 2005-2010.  The whistler finds the plasmapause position which can be clearly allocated in both daytime and nighttime.  We examine the nighttime/daytime plasmapause in various longitudes, solar activities, seasons, and geomagnetic actives.  Results show that the daytime plasmapause appears in the equatorward side of the nighttime one.  Both the daytime and nighttime plasmapause are sensitive to solar activity, which move equatorward form the low to high solar activity in the study period.  The seasonal variation of the plasmapause are rather random and insignificant.  During magnetic disturbed condition, the plasmapause tend to move equatorward.

How to cite: Chen, C.-Y. and Liu, J.-Y.: The Daytime and Nighttime Mapped Whistler Plasmapause Observed by DEMETER, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13485, https://doi.org/10.5194/egusphere-egu2020-13485, 2020.

D1770 |
Sumon Kamal, Norbert Jakowski, Mohammed M. Hoque, and Jens Wickert

Under certain space weather conditions the ionization level of the ionospheric E layer can dominate over that of the F2 layer. This phenomenon is known as “E layer dominated ionosphere” (ELDI) and occurs primarily at high latitudes in the polar regions. The corresponding electron density profiles show their peak ionization at the E layer height between 80 km and 150 km above the Earth’s surface. In this work we have evaluated the influence of space weather and geophysical conditions on the occurrence of ELDI events at high latitudes in the northern and southern hemispheres. For this, we used electron density profiles derived from ionospheric radio occultation measurements aboard CHAMP, COSMIC and FY3C satellites. The used CHAMP data covers the years from 2001 to 2008, the COSMIC data the years from 2006 to 2018 and the FY3C data the years from 2014 to 2018. This provides us continuous data coverage for a long period from 2001 to 2018, containing about 4 million electron density profiles. In addition to the geospatial distribution, we have also investigated the temporal occurrence of ELDI events in the form of the diurnal, the seasonal and the solar activity dependent variation. We have further investigated the influence of geomagnetic storms on the spatial and temporal occurrence of ELDI events.

How to cite: Kamal, S., Jakowski, N., Hoque, M. M., and Wickert, J.: Evaluation of E-Layer Dominated Ionosphere Events Using CHAMP, COSMIC/FORMOSAT-3 and FY3C Data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9382, https://doi.org/10.5194/egusphere-egu2020-9382, 2020.

D1771 |
Daniel Emmons

A multiple phase screen model is used to simulate GPS radio occultation signals through varying sporadic-E layers.  The length, vertical extent, and plasma frequency of the sporadic-E layers are varied to analyze the effect on the signal received by a low earth orbiting satellite.  A nonlinear relationship between the maximum variance in the signal amplitude and the plasma frequency is observed.  For certain frequency ranges, the predictions match previous studies that have used the S4 scintillation index to predict fbEs values. Additionally, the spectra of the signals are analyzed as a function of the different parameters providing an alternative approach for extracting sporadic-E parameters from GPS radio occultation measurements. 

How to cite: Emmons, D.: Simulated GPS radio occultation signals from sporadic-E layers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12026, https://doi.org/10.5194/egusphere-egu2020-12026, 2020.

D1772 |
Ningbo Wang, Zishen Li, and Liang Wang

To enable GNSS applications with low or no time latency, real-time services (RTS) of the International GNSS Services (IGS) has been launched since 2013. The IGS RTS provides real-time data streams with latencies of less than few seconds, containing multi-frequency and multi-constellation GNSS measurements from a global network of high-quality GNSS receivers, which provides the opportunity to reconstruct global ionospheric models in real-time mode. For the computation of real-time global ionospheric maps (RT-GIM), a 2-day predicted global ionospheric model is introduced along with real-time slant ionospheric delays extracted from real-time IGS global stations. GPS and GLONASS L1+L2, BeiDou B1+B2 and Galileo E1+E5a signals with a sampling rate of 1 Hz are used to extract slant TEC (STEC) estimates. Spherical harmonic expansion up to degree and order 15 is employed for global vertical TEC (VTEC) modeling by combining the observed and predicted ionospheric data in real-time mode. Real-time ionospheric State Space Representation (SSR) corrections are then distributed in RTCM 1264 message ( aside from the generation of RT-GIM in IONEX v1.0 format (available at ftp://ftp.gipp.org.cn/product/ionex/). The quality of CAS RT-GIMs is assessed during an 18-month period starting from August 2017, by comparison with GPS differential slant TECs at the selected IGS stations over continental areas, Jason-3 VTECs over the oceans and IGS combined final GIMs on a global scale, respectively. Results show that CAS’s RT-GIM products exhibit a relative error of 13.9%, which is only approximately 1-2% worse than the final ones during the test period. Additionally, the application of RT-GIM on the single-frequency precise point positioning (PPP) of smartphones is also presented.

How to cite: Wang, N., Li, Z., and Wang, L.: IGS RTS for real-time global ionospheric total electron content modeling: Method and Applications, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8281, https://doi.org/10.5194/egusphere-egu2020-8281, 2020.

D1773 |
Zishen Li, Ningbo Wang, Andrzej Krankowski, Xingliang Huo, libo Liu, and Liang Li

In recent years the development of satellite navigation systems sped up and is no longer limited to well-known GPS and GLONASS systems. A good example of which are Europe’s Galileo and China’s BeiDou systems, which can be integrated for various scientific applications. ARTEMIS is a Chinese-Polish joint project concentrating on an important area of space research – space weather monitoring – through the development of new technologies and methods of Earth’s ionosphere monitoring. The main objective of the project is a development of the methodology for ionospheric real-time services using observations from BeiDou, Galileo and GPS systems, which are of extreme importance from professional (precise positioning, satellite navigation) and scientific points of view in the areas requiring current and accurate information on the state of the ionosphere.


The concept of ARTEMIS for real-time ionospheric space weather service is presented at first in this contribution, followed by the scientific progress from both Chinese and Polish sides during the year 2019. Benefiting from the real-time multi-constellation and multi-frequency GNSS data streams from regional and global permanent network stations, a prototype service system for real-time ionospheric monitoring was developed, which supports at current stage, the generation of global real-time Total Electron Content (TEC) maps, global Rate of TEC Index (ROTI) maps, as well as regional TEC/ROTI maps over Chinese and European regions. Using the home-made ionospheric scintillation (IS) monitoring receiver, i.e. BDSMART, an experimental campaign was carried out at low-latitude stations of China for the quality examination of BDSMART IS receivers. The ionospheric scintillation monitoring results from both GNSS L band and Low Frequency Array (LOFAR) low-frequency radio astronomical observations are highlighted by the Polish partner. The Chinese low-latitude Ionospheric Experimental Network (CHINE) for low-latitude ionospheric scintillation monitoring is now under construction. The generation of regional and global three-dimensional ionospheric electron densities in real-time is still in progress.

How to cite: Li, Z., Wang, N., Krankowski, A., Huo, X., Liu, L., and Li, L.: ARTEMIS: Advanced methodology development for Real-TimE Multi-constellation (BDS, Galileo and GPS) Ionosphere Services, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8770, https://doi.org/10.5194/egusphere-egu2020-8770, 2020.

D1774 |
Yang Liu, Zheng Li, and Jinling Wang

A series of studies have suggested that a geomagnetic storm can accelerate the formation of plasma depletions and the generation of ionospheric irregularities. Using observation data from the Continuously Operating Reference Stations (CORS) network in the USA, the responses of the ionospheric total electron content (TEC) to the geomagnetic storm on September 8, 2017 are studied in detail. A mid-latitude trough was discovered from 01:00 UT to 06:00 UT in the USA with a length exceeding 5000 km. The probable causes are the combination of a classic negative storm response with increments in the neutral composition and the expansion of the auroral oval, pushing the mid-latitude trough equatorward.  Super-scale plasma depletion was observed by SWARM data accompanied by the expansion of mid-latitude trough. Both PPEF from high latitudes and pole-ward neutral wind are responsible for the large-scale ionospheric irregularities. Medium-scale travelling ionospheric disturbances (MSTID) with wavelengths of 600–700 km were generated accompanied by a drop and perturbation in the electron density. The intensity of the MSTID fluctuations reached over 2.5 TECU, which were discovered by filtering the differential TEC. The evolution of plasma depletions were associated with the MSTID propagating from high latitudes to low latitudes. SWARM spaceborne observations also showed a drop in the electron density from 105 to 103 compared to the background values at 28° N, 96° W, and 25° N, 95° W. This research investigates super-scale plasma depletions generated by geomagnetic storms using both CORS GNSS and spaceborne observations. The proposed work is valuable for better understanding the evolution of ionospheric depletions during geomagnetic storms.

How to cite: Liu, Y., Li, Z., and Wang, J.: Studying the Ionospheric Responses Induced by a Geomagnetic Storm in September 2017 with Multiple Observations in America, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1906, https://doi.org/10.5194/egusphere-egu2020-1906, 2020.

D1775 |
Sandro Krauss, Manuela Temmer, Saniya Behzadpour, and Christoph Lhotka

On August 20, 2018 a complex interplanetary coronal mass ejections (ICME) occurred on the Sun, which subsequently triggered an unexpected large geomagnetic storm on August 25. We present a detailed analysis of the ICME eruption and explore the occurred perturbation of the neutral mass density in the upper Earth's atmosphere. The analysis is based on accelerometer observations from the satellite mission GRACE Follow-On as well as interplanetary magnetic field measurements by the DSCOVR and ACE spacecraft. Through the evaluation of solar observations by the SECCHI instrument on-board of the STEREO-A satellite in form of white-light, the early evolution of the ICME can be aptly illustrated. Furthermore, due to the heating and the subsequent expansion of the thermosphere also the drag force acting on the spacecraft is enhanced. This leads to an additional storm induced orbit decay, which we calculate by means of variations in the semi-major axis. The findings are compared with predictions from our preliminary thermospheric forecasting tool, which is based on the study by Krauss et al. 2018.

How to cite: Krauss, S., Temmer, M., Behzadpour, S., and Lhotka, C.: Analysis of a severe geomagnetic storm on August 26, 2018 and the related effects on the GRACE-FO mission, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3499, https://doi.org/10.5194/egusphere-egu2020-3499, 2020.

D1776 |
Tatiana Výbošťoková, Michal Švanda, and Zdeněk Němeček

Eruptive events on the Sun interacts with the magnetosphere and can affect even the Earth-bound structures such as power transmission networks via geomagnetically induced electric currents (GICs). We quantify the geomagnetic activity by the K-index computed from local measurements of the geomagnetic field and investigate its effects on the Czech electric power grid represented as disturbances recorded in the maintenance logs of the power network operators in course of last 12 years. In data sets recording the disturbances on high and very high voltage power lines, we found a statistically significant increase of anomaly rates within tens of days around maxima of a geomagnetic activity compared to the adjacent activity minima. Moreover, we modeled GICs for two (east-west and north-south oriented) high-voltage transmission lines in the Czech Republic and found surprisingly high values of currents, in the order of tens of amperes. Based on in-situ observations, we study propagation and properties of the largest CMEs and their relation to the disturbances in the transmission networks of the Central European countries. Our results provide an evidence that GICs may affect the occurrence rate of anomalies registered on power-grid equipment even in the mid-latitude countries.

How to cite: Výbošťoková, T., Švanda, M., and Němeček, Z.: Geomagnetically induced currents in central Europe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3694, https://doi.org/10.5194/egusphere-egu2020-3694, 2020.

D1777 |
Paul Song and Jian-Nan Tu

We study the polar magnetospheric coupling to the ionosphere/thermosphere and ground system along the field by examining a spectrum of perturbations propagating from the magnetosphere downward. What distinguishes this study from conventional treatments of the magnetosphere-ionosphere/thermosphere system is that our treatment self-consistently includes the responses of the neutrals to the magnetic and plasma velocity perturbations. The thermosphere is coupled to the magnetosphere-ionosphere (M-I) system in a degree that depends on the time scale of the perturbations. There are three major processes that affect the perturbation propagation: damping that reduces the energy flux while producing heating, the neutral-inertia loading that reduces the propagation speed, and reflection which, associated with structures of the ionosphere and thermosphere, reduces the downward energy flux. The damping is stronger in higher frequencies, 10-2~0 Hz for M-I coupling. As a result of reflection, significant energy fluxes of the magnetospheric perturbations cannot reach the lower ionosphere and hence the ground although some heating and energization may occur in the lower ionosphere resulting from the strong damping of high frequency fluctuations. However, the amplitude of the magnetic fluctuations of the transmitted flux into the lower ionosphere can be enhanced in lower frequencies because of the decrease in the propagation speed due to strong neutral-inertia loading. Combining the attenuation and amplitude enhancement effects, the net enhanced amplitudes occur in frequencies less than few Hertz, which may explain the ready observations of PC waves that are enhanced magnetic oscillations in periods from 0.5 sec to 30 min on the ground while little enhancement is observed below this period range. On the other hand, the smallness of the propagation velocity results in very small electric perturbations, forming a magneto-static condition for coupling from the lower ionosphere to the ground in low-frequencies, casting doubts on any ionosphere-ground coupling mechanisms based on static electric field in the lower frequencies.

How to cite: Song, P. and Tu, J.-N.: How the magnetosphere-ionosphere/thermosphere-ground system is coupled by waves, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10986, https://doi.org/10.5194/egusphere-egu2020-10986, 2020.

D1778 |
Rui Song, Katsumi Hattori, and Chie Yoshino

  The three-dimensional (3-D) tomographic inversion is a crucial technique for imaging the ionospheric electron distributions (IEDs) on both the horizontal and vertical directions based on the total electron content (TEC) data. In this study, a regional 3-D tomography was realized in Japan using the Kalman Filter (KF) algorithm. In addition, to deduce the divergences, the adaptive Sage-Husa KF (SHKF) was proposed to determine the unknown priori information of the noise covariance encountered in the conventional KF (CKF). From this base, slant TEC (STEC) data observed by 55 GPS (Global Positioning System) receivers in the years of 2013 and 2018 was selected for IED reconstructions with the resolution 1º×1º×30 km in latitude, longitude and altitude, respectively. As for the ionospheric diurnal and annual variations, by comparing the F2 layer peak electron density (NmF2) simulated by SHKF, CKF, and the International Reference Ionosphere (IRI) model with the observed values detected by 4 Japanese ionosondes (Okinawa, Yamagawa, Kokubunji, and Wakkanai) during April 3-9, 2018 and 2013, the Root-Mean-Square-Error (RMSE) and co-releation index (ρ) were adopted to evaluate the simulated effciency. Results showed that the least RMSE (0.3084 in 2018, 0.5397 in 2013) and the best ρ values (0.9517 in 2018, 0.9896 in 2013) were both given by the SHKF-CIT method. Then, seasonal characteristics were implemented on January 02, March 20, June 14 and September 24, 2018, where the variations of northern EIA, winter and semiannual anomalies were accurately captured by the SHFK method. Meanwhile, the recalculated TEC values as well as the inverted vertical profiles manifested that SHKF-based tomography was outperformed the other methods. In the end, taking a strong geomagnetic storm happened on 26 August, 2018 as an example, both the meridional and latitudinal (along 135°E and 35°N, respectively) IEDs displayed more significant promotions than IRI model, and the results indicates that the IED around Japan developed by SHKF-based tomography is promising for the ionospheric studies and practical applications.

How to cite: Song, R., Hattori, K., and Yoshino, C.: The three-dimensional ionospheric tomography in Japan by using the adaptive Kalman Filter algorithm, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12646, https://doi.org/10.5194/egusphere-egu2020-12646, 2020.

D1779 |
Grzegorz Nykiel, Yevgen Zanimonskiy, Mariusz Figurski, Zofia Baldysz, Aleksander Koloskov, and Andrey Sopin

The coupling of the ionosphere with the tropospheric processes is a complex problem and the necessity of its resolve is highlighted in numerous publications. They mainly focus on lightning, hurricanes, tornadoes, as well as tsunamis, which induce disturbances in the ionosphere. Current works suggest that they are generated by the two major mechanisms: electrical effects during lightning, and atmospheric gravity waves propagated vertically and horizontally. However, these mechanisms are still not precisely examined.

The aim of this study is investigation of the coupling of severe weather event with ionosphere. This phenomenon, which can be classified as derecho occurred on 11th August 2017 in Poland. It was a 300 km length bow echo heavy storm, characterized by wind gusts of about 150 km/h, lightning, strong rain and hail drops. All these factors may have caused disturbances not only in the troposphere but also affect the ionosphere. In order to investigate a coupling mechanism and determination of morphological characteristics of the ionospheric disturbances, we used a dense network of GNSS receivers. Using GPS and GLONASS observations, we estimated total electron content (TEC) variations with 30-second interval. This has allowed to obtain high spatial and temporal resolution maps of ionospheric disturbances which have been compared with other data derived from in situ meteorological measurements, weather radars, and the Weather Research and Forecasting (WRF) numerical weather model. We investigated that during the main phase of the storm the wavy-like ionospheric disturbances occurred for some of the observed satellite with magnitude of about 0.2 TECU. In this work, we present detailed analysis of this event and discussion about troposphere-ionosphere coupling.

How to cite: Nykiel, G., Zanimonskiy, Y., Figurski, M., Baldysz, Z., Koloskov, A., and Sopin, A.: Analysis of ionospheric disturbances caused by the severe weather event in Poland on 11th August 2017, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13348, https://doi.org/10.5194/egusphere-egu2020-13348, 2020.

D1780 |
wen zhang, xingliang Huo, and haojie Liu

Ionosphere is one of the main errors in the signal propagation of global navigation system satellite (GNSS), and it is also the key issue of space weather. The International Reference Ionosphere (IRI) is the most important empirical model described the ionospheric characteristics, and it provides the monthly averages of electron densities and vertical total electron content (VTEC) in the altitude range of 50km-2000km. The IRI-2016 model is the latest version. But some studies showed that the accuracy of the IRI model is not high enough in China due to the use of fewer data sources. This paper will assess the performance of IRI-2016 model in China, and a modified IRI 2016 model by adjusting the driving parameters IG and RZ index of IRI2016 model with GNSS TEC data are also investigated. In this contribution, GNSS data from the Crustal Movement Observation Network of China (CMONC) are used to estimate TEC values, and the ionosonde data from three stations are used as references for the ionospheric electron densities. Three ionosonde stations are located at Beijing (BP440, 40.3°N/116.2°E), Wuhan (WU430, 30.5°N/114.4°E) and Sanya (SA418, 18.3°N/ 109.6°E). The above data respectively cover a period of 6 days in the high year (2015) and low year (2019) of solar activity.

The study shows that the biggest reason for the difference (DTEC) between GPS-TEC and IRI2016-TEC in China is that the poor estimation of NmF2 and hmF2 by IRI model, and the driving parameters IG and RZ index of IRI2016 can be updated by constraining DTEC. Finally, the performance of the modified IRI-2016 model is improved by the updated IG and RZ indexes as the short-term driving values of ionospheric parameters. The analysis show that the modified IRI-2016 model is more accurate at estimating both the TEC and the electron density profile than the original model.

How to cite: zhang, W., Huo, X., and Liu, H.: Assessment of the IRI-2016 and modified IRI 2016 models in China: Comparison with GNSS-TEC and ionosonde data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16646, https://doi.org/10.5194/egusphere-egu2020-16646, 2020.

D1781 |
Paulina Woźniak, Anna Świątek, Mariusz Pożoga, and Łukasz Tomasik

The signal emitted by the GNSS (Global Navigation Satellite System) satellite, on the way to the receiver located on the Earth’s surface, encounters a heterogeneous layer of ionized gas and free electrons, in which the radio wave is dispersed. As the ionosphere is the source of the highest-value errors among the different factors that affect GNSS positioning accuracy, it is necessary to minimize its negative impact. Various methods are used to compensate for the ionospheric delay, one of which is the usage of models.
The intensity of the processes occurring in the ionosphere is closely related to the Sun activity. As a consequence, with respect to a given location on the Earth's surface, the activity of the ionosphere changes throughout the year and day. Therefore, a model dedicated to a specific region is especially important in case of high-precision GNSS applications.
The assimilated H2PT model was based on the dual-frequency observations from GNSS stations belonging to EPN (EUREF Permanent Network), as well as on ionosondes participating in the DIAS (European Digital Upper Atmosphere Server) project. The H2PT model covers the Europe area, data with a 15-minutes interval were placed in similar to IONEX (IONosphere Map EXchenge) files in two versions of spatial resolution: 1- and 5-degree. Data provided by the H2PT model are the VTEC (Vertical Total Electron Content) values and the hmF2 (maximum height of the F2 layer) parameters.
The subject of this research is the comparison of the H2PT model with NeQuick-G model and IONEX data published by IGS (International GNSS Service) in the context of TEC values as well as determining differences between regional hmF2 data and its commonly used fixed value for the entire globe, amounting to 450 km. In order to perform the analysis, appropriate visualizations were made and statistical parameters determined. Additionally, data from selected periods of positive and negative disturbances were analysed in details based on the developed time series.
The relatively high temporal and spatial resolution is undoubtedly an advantage of the H2PT model, because unlike global models, the regional one allows conscientious analysis of the ionosphere characteristics for the area of Europe. Importantly, solutions regarding hmF2 show significant deviations from the fixed value approximated for the whole Earth. Taking into account the parameter appropriate for a given location and time during GNSS data processing may improve the obtained positioning quality. 

How to cite: Woźniak, P., Świątek, A., Pożoga, M., and Tomasik, Ł.: Analysis of a new regional ionospheric assimilated H2PT model for Europe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1524, https://doi.org/10.5194/egusphere-egu2020-1524, 2020.

D1782 |
Randa Natras and Andreas Goss

The ionospheric delay is one of the main error-sources in applications that rely on the Global Navigation Satellite System (GNSS) observations. Dual-frequency receivers allow the elimination of the major part of the ionospheric range error by forming an ionosphere-free linear combination (L3). However, although global models broadcasted by the satellite systems are available, single-frequency mass-market receivers are not able to correct the signal’s delay with sufficient accuracy and precise regional ionosphere models are necessary. Today no regional ionosphere models, based on the national GNSS/GPS infrastructure, are available in the Western Balkans countries.

In this study, an ionosphere vertical total electron content (VTEC) model IONO_WB is derived from dual-frequency GPS observations of Continuously Operating Reference Stations (CORS) belonging to the following positioning networks: ALPBOS and IGEWE (Albania), BIHPOS (Bosnia and Herzegovina), CROPOS (Croatia), MAKPOS (North Macedonia), and SIGNAL (Slovenia). In addition, observations from 8 permanent stations of the EUREF Permanent Network (EPN) in this region are used. The chosen network comprises in total about 70 CORS and EPN stations in the range from about 40⁰ N to 47⁰ N and 13⁰ E to 23⁰ E. The estimation of the ionosphere VTEC model parameters is based on the geometry-free (L4) linear combination of phase (zero-difference) observations. The ionosphere is approximated by a single-layer model at a height of 450 km. TEC modelling is performed by two-dimensional Taylor series expansions in a Sun-fixed reference frame with a degree and order of 2 and a temporal resolution of 1 hour. Corrections for positioning with a single frequency (L1) are estimated and evaluated in positioning application. Data processing, model estimation and positioning evaluation are performed in the Bernese GNSS Software v.5.2

The developed ionosphere IONO_WB model is tested for periods of the solar maximum (March 2014) and the St. Patrick´s geomagnetic storm (March 2015). For validation purposes, the model is compared to Global Ionosphere Maps (GIM) issued by the IGS Associate Analysis Centers (CODE, ESA/ESOC, JPL, gAGE/UPC) and the regional high-resolution VTEC maps from DGFI-TUM realized as multi-scale B-spline representations. The model`s applicability is evaluated with single-frequency positioning, where selected EPN and CORS stations are processed applying the corrections estimated from the regional model IONO_WB. Resulting 3D position errors (RMS) were in most cases at least 20% to 50% lower compared to CODE ionosphere products during high solar activity and severe geomagnetic storm.

How to cite: Natras, R. and Goss, A.: Regional Ionosphere VTEC Modelling and Application for Single-Frequency Positioning in the Western Balkans, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19166, https://doi.org/10.5194/egusphere-egu2020-19166, 2020.

D1783 |
Saurav Aryal, J. Scott Evans, Stanley C. Solomon, Alan G. Burns, John Correira, Tong Dang, Jiuhou Lei, Geonhwa Jee, Huixin Liu, Wenbin Wang, and Richard W. Eastes

NASA’s Global-scale Observation of Limb and Disk’s (GOLD) instrument observed the July 2, 2019 total solar eclipse’s effect in the thermosphere from a geostationary orbit above South America. GOLD’s observations of compositional and neutral temperature changes induced by the eclipse are different from the modeled effects. Combined Thermospheric Ionospheric Electrodynamics General Circulation Model (TIE-GCM) and GLobal airglOW (GLOW) modeling of GOLD’s observation is relatively successful in reproducing morphologically changes. However, the model underestimates the compositional changes. GOLD observation show a ΣO/N2 column density ratio enhancement of ~ 80 % near the totality, but the model predicts ~ 10 % enhancement. This indicates that there are inadequacies in current modeling capabilities for thermospheric changes during an eclipse. GOLD’s thermospheric measurements provide an important, new test of the models. We will present detailed data-model comparisons of measurements versus modeling results for the July 2nd eclipse.

How to cite: Aryal, S., Evans, J. S., Solomon, S. C., Burns, A. G., Correira, J., Dang, T., Lei, J., Jee, G., Liu, H., Wang, W., and Eastes, R. W.: Global-scale data-model comparison of the July 2nd, 2019 total solar eclipse’s thermospheric effect , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13197, https://doi.org/10.5194/egusphere-egu2020-13197, 2020.

D1784 |
Anders M. Jorgensen, An Ngoc, Kyler King, Willie Lopez, Alexander Mazarakis, Leviy Jungling, Wesley McHaley, Delos Edick, and Richard Sonnenfeld

We present the Flexible Radio Array for Ionospheric and Atmospheric
research (FRAIA). FRAIA consists of 18 relocatable RF receiver
stations with the capability to receive in the VLF band (0-50 kHz),
the HF/VHF band (3-85 MHz), as well as at discrete beacon satellite
frequencies 150, 400, and 1067 MHz. The antennas are monopole for the
VLF reception, all-sky broad-band crossed dipoles for the HF/VHF band,
and co-centric all-sky quadrifilar antennas for the beacon satellite
bands. Each station contains a 8-core CPU and a high-end
software-defined radio for real-time sampling and processing of the RF
signals. Each station include GPS timing to 50 ns, and three
synchronization devices allows for the 18 stations to be used together
in a single phased array or up to three phased arrays. FRAIA stations
can be used for observing VLF whistler waves, receiving standard
VHF/UHF beacon satellite signals for ionospheric tomography, for
riometry, for lightning observations and lightning interferometry, as
ionosonde receivers, HF radar receivers, over-the-horizon radar
receivers, and receivers for a future HF beacon satellite which we
propose, for ionospheric tomography.

How to cite: Jorgensen, A. M., Ngoc, A., King, K., Lopez, W., Mazarakis, A., Jungling, L., McHaley, W., Edick, D., and Sonnenfeld, R.: Flexible Radio Array for Ionospheric and Atmospheric research (FRAIA), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20867, https://doi.org/10.5194/egusphere-egu2020-20867, 2020.

D1785 |
Hossein Ghadjari, David Knudsen, and Susan Skone

Ionospheric irregularities are fluctuations or structures of plasma density that affect the propagation of radio signals. Whenever large-scale irregularities break up into meso and small-scale irregularities, these processes become similar to a turbulence cascade. In order to have a better comparison between this and plasma density irregularities, we study different orders of structure functions of plasma density of total loss of lock events measured with the faceplate measurements of plasma density and the GPS measurements from the Swarm mission. Total loss of lock of GPS signal is a physical proxy for severe degradation of GPS signals. In addition to different orders of structure-function, we study the existence of self-similarity or multifractality of plasma density of total loss of lock events to investigate any possible intermittent fluctuations. 

How to cite: Ghadjari, H., Knudsen, D., and Skone, S.: Structure function analysis of plasma density fluctuations during total loss of lock of GPS signal events, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11622, https://doi.org/10.5194/egusphere-egu2020-11622, 2020.

D1786 |
Min Li, Baocheng Zhang, and Xiao Zhang

When sensing the Earth’s ionosphere using pseudorange observations of global navigation satellite systems (GNSS), the satellite and receiver Differential Code Biases (DCBs) account for one of the main sources of error. For the sake of convenience, Receiver DCBs (DCBs) are commonly assumed as constants over a period of one day in the traditional carrier-to-code leveling (CCL) method. Thus, remarkable intraday variability in the receiver DCBs have been ignored in the commonly-used assumption and may seriously restrict the accuracy of ionospheric observable retrieval. The Modified CCL (MCCL) method can eliminate the adverse impact of the short-term variations of RDCBs on the retrieval of ionospheric TEC. With the rapid development of the GPS, GLONASS, Galileo and BeiDou systems, there is a strong demand of precise ionospheric TEC products for multiple constellations and frequencies. Considering the existed MCCL method can only be used for dual-frequency GNSS data, in this study, we extend the two-frequency MCCL method to the multi-frequency and multi-GNSS case and further carry out a series of investigations. In our proposed method, a newly full-rank multi-frequency (more than triple frequency) model with raw observations are established to synchronously estimate both the slant ionospheric delays and the RCB offset with respect to the reference epoch at each individual frequency. Based on the test results, compared to the traditional CCL-method, the accuracy of the ionospheric TEC retrieved using our proposed method can be improved from 5.12 TECu to 0.95 TECu in the case that significant short-term variations existed in receiver DCBs. In addition, the between-epoch fluctuations experienced by receiver code biases at all frequencies tracked by a single receiver can be detected by our the proposed method, and the dependence of multi-GNSS and multi-frequency RDCB offsets upon ambient temperature further are verified in this study. Compared to Galileo system, the RDCB in BDS show higher correlation with temperature. We also found that the RDCB at different frequencies of the same system show various characteristics.

How to cite: Li, M., Zhang, B., and Zhang, X.: Determation of the ionospheric observable and short-term variations of receiver DCBs using modified carrier‑to‑code leveling method with multi-frequency and multi-GNSS data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20967, https://doi.org/10.5194/egusphere-egu2020-20967, 2020.