scholarly journals Analysis of different propagation models for the estimation of the topside ionosphere and plasmasphere with an ensemble Kalman filter

2020 ◽  
Vol 38 (6) ◽  
pp. 1171-1189
Author(s):  
Tatjana Gerzen ◽  
David Minkwitz ◽  
Michael Schmidt ◽  
Eren Erdogan
Keyword(s):  
Kalman Filter ◽  
Electron Density ◽  
Ensemble Kalman Filter ◽  
Propagation Model ◽  
Topside Ionosphere ◽  
Reconstruction Technique ◽  
Electron Content ◽  
Propagation Models ◽  
Total Electron ◽  
Swarm Satellites

Abstract. The accuracy and availability of satellite-based applications, like Global Navigation Satellite System (GNSS) positioning and remote sensing, crucially depend on the knowledge of the ionospheric electron density distribution. The tomography of the ionosphere is one of the major tools for providing links to specific ionospheric corrections and studying and monitoring physical processes in the ionosphere and plasmasphere. In this work, we apply an ensemble Kalman filter (EnKF) approach for the 4D electron density reconstruction of the topside ionosphere and plasmasphere, with the focus on the investigation of different propagation models, and compare them with the iterative reconstruction technique of simultaneous multiplicative column normalized method plus (SMART+). The slant total electron content (STEC) measurements of 11 low earth orbit (LEO) satellites are assimilated into the reconstructions. We conduct a case study on a global grid with altitudes between 430 and 20 200 km, for two periods of the year 2015, covering quiet to perturbed ionospheric conditions. Particularly the performance of the methods for estimating independent STEC and electron density measurements from the three Swarm satellites is analysed. The results indicate that the methods of EnKF, with exponential decay as the propagation model, and SMART+ perform best, providing, in summary, the lowest residuals.

scholarly journals Analyses of different propagation models for the estimation of the topside ionosphere and plasmasphere with an Ensemble Kalman Filter

2020 ◽  
Author(s):  
Tatjana Gerzen ◽  
David Minkwitz ◽  
Michael Schmidt ◽  
Eren Erdogan
Keyword(s):  
Kalman Filter ◽  
Electron Density ◽  
Ensemble Kalman Filter ◽  
Propagation Model ◽  
Topside Ionosphere ◽  
Reconstruction Technique ◽  
Propagation Models ◽  
Swarm Satellites ◽  
Iterative Reconstruction Technique

Abstract. The accuracy and availability of satellite-based applications like GNSS positioning and remote sensing crucially depends on the knowledge of the ionospheric electron density distribution. The tomography of the ionosphere is one of the major tools to provide link specific ionospheric corrections as well as to study and monitor physical processes in the ionosphere and plasmasphere. In this work, we apply an Ensemble Kalman Filter (EnKF) approach for the 4D electron density reconstruction of the topside ionosphere and plasmasphere with the focus on the investigation of different propagation models and compare them with the iterative reconstruction technique SMART+. The STEC measurements of eleven LEO satellites are assimilated into the reconstructions. We conduct a case study on a global grid with altitudes between 430 and 20200 km, for two periods of the year 2015 covering quiet to perturbed ionospheric conditions. Particularly, the performance of the methods to estimate independent STEC and electron density measurements from the three Swarm satellites is analysed. The results indicate that the methods EnKF with Exponential decay as the propagation model and SMART+ perform best, providing in summary the lowest residuals.

scholarly journals Plasmasphere and Topside Ionosphere Reconstruction using METOP Satellite Data during Geomagnetic Storms

2020 ◽  
Author(s):  
Fabricio dos Santos Prol ◽  
Mainul Hoque ◽  
Arthur Amaral Ferreira
Keyword(s):  
Electron Density ◽  
Space Weather ◽  
Geomagnetic Storms ◽  
Tomographic Reconstruction ◽  
Satellite System ◽  
Low Earth Orbit ◽  
Topside Ionosphere ◽  
Reconstruction Technique ◽  
Electron Content ◽  
Total Electron

As part of the space weather monitoring, the response of the ionosphere and plasmasphere to geomagnetic storms is typically under continuous supervision by operational services. Fortunately, Global Navigation Satellite System (GNSS) receivers on board low Earth orbit satellites provides a unique opportunity for developing image representations that can capture the global distribution of the electron density in the plasmasphere and topside ionosphere. Among the difficulties of plasmaspheric imaging based on GNSS measurements, the development of procedures to invert the Total Electron Content (TEC) into electron density distributions remains as a challenging task. In this study, a new tomographic reconstruction technique is presented to estimate the electron density from TEC data along the METOP (Meteorological Operational) satellites. The proposed method is evaluated during four geomagnetic storms to check the capabilities of the tomography for space weather monitoring. The investigation shows that the developed method can successfully capture and reconstruct well-known enhancement and decrease of electron density variabilities during storms. The comparison with in-situ electron densities has shown an improvement around 11% and a better description of plasma variabilities due to the storms compared to the background. Our study also reveals that the plasmasphere TEC contribution to ground-based TEC may vary 10 to 60% during geomagnetic storms, and the contribution tends to reduce during the storm-recovery phase

scholarly journals Topside Ionosphere and Plasmasphere Modelling Using GNSS Radio Occultation and POD Data

2021 ◽  
Vol 13 (8) ◽  
pp. 1559
Author(s):  
Fabricio S. Prol ◽  
M. Mainul Hoque
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
Radio Occultation ◽  
Geomagnetic Latitude ◽  
Low Earth Orbit ◽  
Activity Level ◽  
Topside Ionosphere ◽  
Electron Content ◽  
Total Electron ◽  
Solar Activity Level

A 3D-model approach has been developed to describe the electron density of the topside ionosphere and plasmasphere based on Global Navigation Satellite System (GNSS) measurements onboard low Earth orbit satellites. Electron density profiles derived from ionospheric Radio Occultation (RO) data are extrapolated to the upper ionosphere and plasmasphere based on a linear Vary-Chap function and Total Electron Content (TEC) measurements. A final update is then obtained by applying tomographic algorithms to the slant TEC measurements. Since the background specification is created with RO data, the proposed approach does not require using any external ionospheric/plasmaspheric model to adapt to the most recent data distributions. We assessed the model accuracy in 2013 and 2018 using independent TEC data, in situ electron density measurements, and ionosondes. A systematic better specification was obtained in comparison to NeQuick, with improvements around 15% in terms of electron density at 800 km, 26% at the top-most region (above 10,000 km) and 26% to 55% in terms of TEC, depending on the solar activity level. Our investigation shows that the developed model follows a known variation of electron density with respect to geographic/geomagnetic latitude, altitude, solar activity level, season, and local time, revealing the approach as a practical and useful tool for describing topside ionosphere and plasmasphere using satellite-based GNSS data.

scholarly journals Topside ionospheric vertical electron density profile reconstruction using GPS and ionosonde data: possibilities for South Africa

2011 ◽  
Vol 29 (2) ◽  
pp. 229-236 ◽  
Author(s):  
P. Sibanda ◽  
L. A. McKinnell
Keyword(s):  
South Africa ◽  
Electron Density ◽  
Geographic Location ◽  
Electron Density Profile ◽  
Empirical Modeling ◽  
Topside Ionosphere ◽  
Electron Content ◽  
Total Electron ◽  
Gps Tec ◽  
Profile Reconstruction

Abstract. Successful empirical modeling of the topside ionosphere relies on the availability of good quality measured data. The Alouette, ISIS and Intercosmos-19 satellite missions provided large amounts of topside sounder data, but with limited coverage of relevant geophysical conditions (e.g., geographic location, diurnal, seasonal and solar activity) by each individual mission. Recently, methods for inferring the electron density distribution in the topside ionosphere from Global Positioning System (GPS)-based total electron content (TEC) measurements have been developed. This study is focused on the modeling efforts in South Africa and presents the implementation of a technique for reconstructing the topside ionospheric electron density (Ne) using a combination of GPS-TEC and ionosonde measurements and empirically obtained Upper Transition Height (UTH). The technique produces reasonable profiles as determined by the global models already in operation. With the added advantage that the constructed profiles are tied to reliable measured GPS-TEC and the empirically determined upper transition height, the technique offers a higher level of confidence in the resulting Ne profiles.

scholarly journals Positive ionospheric storm effects at Latin America longitude during the superstorm of 20–22 November 2003: revisit

2012 ◽  
Vol 30 (5) ◽  
pp. 831-840 ◽  
Author(s):  
B. Zhao ◽  
W. Wan ◽  
J. Lei ◽  
Y. Wei ◽  
Y. Sahai ◽  
...  
Keyword(s):  
Latin America ◽  
Electron Density ◽  
Topside Ionosphere ◽  
Electron Content ◽  
South American ◽  
Ionospheric Storm ◽  
The South ◽  
Total Electron ◽  
Storm Effects ◽  
Low Latitudes

Abstract. Positive ionospheric storm effects that occurred during the superstorm on 20 November 2003 are investigated using a combination of ground-based Global Positioning System (GPS) total electron content (TEC), and the meridian chain of ionosondes distributed along the Latin America longitude of ~280° E. Both the ground-based GPS TEC and ionosonde electron density profile data reveal significant enhancements at mid-low latitudes over the 280° E region during the main phase of the November 2003 superstorm. The maximum enhancement of the topside ionospheric electron content is 3.2–7.7 times of the bottomside ionosphere at the locations of the ionosondes distributed around the mid- and low latitudes. Moreover, the height of maximum electron density exceeds 400 km and increases by 100 km compared with the quiet day over the South American area from middle to low latitudes, which might have resulted from a continuous eastward penetration electric field and storm-generated equatorward winds. Our results do not support the conclusions of Yizengaw et al. (2006), who suggested that the observed positive storm over the South American sector was mainly the consequence of the changes of the bottomside ionosphere. The so-called "unusual" responses of the topside ionosphere for the November 2003 storm in Yizengaw et al. (2006) are likely associated with the erroneous usage of magnetometer and incomplete data.

A sequential calibration technique to improve IRI using TEC estimates of the GNSS network in Europe

2021 ◽  
Author(s):  
Ehsan Forootan ◽  
Mona Kosary ◽  
Saeed Farzaneh ◽  
Maike Schumacher
Keyword(s):  
Kalman Filter ◽  
Total Electron Content ◽  
Ensemble Kalman Filter ◽  
Satellite System ◽  
Electron Content ◽  
Dual Frequency ◽  
Iri Model ◽  
Total Electron ◽  
Wide Range ◽  
Point Positioning

<p>The development of space-geodetic observation techniques has brought out a wide range of applications such as positioning and navigation, where the Global Navigation Satellite System (GNSS) is the main tools to provide surveying measurements in these applications. Though GNSS signals enable the calculation of receiver's position, some errors restrict their accuracy. Among these errors, the ionospheric delay is considered as an important error source in the Standard Point Positioning (SPP) applications. Empirical ionospheric models such as Klobuchar, International Reference Ionosphere (IRI), and NeQuick are often applied for computing the Total Electron Content (TEC) within ionosphere and its equivalent delays. However the simulation and forecasting skills of these models are limited due to the simplified model structures and model sensitivity to the calibration period. In this study, we present a novel sequential Calibration approach based on the Ensemble Kalman Filter (C-EnKF) to improve the performance of TEC estimations for SPP applications. To demonstrate the results, the IRI model is used as our basis and the TEC estimates from 56 IGS stations in Europe are applied as observation. The C-EnKF is applied to calibrate some selected model parameter so that IRI can be tuned over Europe. The numerical assessments are performed against the TEC estimates from dual frequency GNSS measurements and against the final IONEX products (that are available with 11 days delays). Based on the forecasting results (during September 2017), we show that the accuracy of TEC estimates from the C-EnKF is improved in the range of 3.7-64.87% compared to IRI. <strong>Keywords: </strong>Ionosphere, Sequential Calibration, Ensemble Kalman Filter (EnKF), IRI, Total Electron Content (TEC), Standard Point Positioning (SPP), GNSS</p>

scholarly journals Modeling of Topside Ionosphere and Plasmasphere

2021 ◽  
Author(s):  
Shigeto Watanabe ◽  
Yoshizumi Miyoshi ◽  
Fuminori Tsuchiya ◽  
Atsusi Kumamoto ◽  
Yoshiya Kasahara ◽  
...  
Keyword(s):  
Electron Density ◽  
3D Structure ◽  
Geomagnetic Latitude ◽  
Time History ◽  
Topside Ionosphere ◽  
Electron Content ◽  
Machine Learning Technique ◽  
Total Electron ◽  
Learning Technique ◽  
Tip Model

Abstract We developed a new topside ionosphere and plasmasphere model using a machine learning technique using approximately five million electron density datasets from the Japanese satellites, namely, Hinotori, Akebono, and Arase. The topside ionosphere and plasmasphere model (TIP-model) can estimate electron densities at altitudes ranging from 500 km to 30,000 km in terms of latitude, longitude, universal time, season, and solar and magnetic activities with time history. The model shows the time-dependent 3D structure of the plasmasphere in response to solar and magnetic activities. The constructed TIP-model reproduces plasmapause, plasma tail/erosion of the plasmasphere, and the plasma escape near the magnetic pole. The total electron content (TEC) in the plasmasphere was also obtained through the integration of electron density from 2,000 km to 30,000 km altitudes. The TEC of the plasmasphere is approximately 5 TECU near the magnetic equator, and it depends strongly on geomagnetic latitude, longitude, local time, and solar and magnetic activities.

Analysis of Swarm Electric Field Data in View of Tsunami Events and related Earthquakes

2020 ◽  
Author(s):  
Wojciech Jarmolowski ◽  
Pawel Wielgosz ◽  
Anna Krypiak-Gregorczyk ◽  
Beata Milanowska
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Electron Content ◽  
Langmuir Probes ◽  
Time And Space ◽  
Total Electron ◽  
Swarm Satellites ◽  
High Orbit ◽  
Orbital Height

<p>Three Swarm satellites are equipped with Langmuir Probes (LP) measuring in-situ electron density of Earth electric field and POD GNSS receivers determining topside total electron content (TEC) in the upper ionosphere. It is proved that different events on the Earth and in its atmopshere have their own impact on Earth electric field, and the earthquakes are in this group. Many strong earthquakes induce tsunamis, which are also suspected as contributing to the gravity waves having an impact on the ionospheric TEC. These reasons encourage to the study on the sensitivity of Swarm LP and POD GNSS data to the abovementioned phenomena. Referring to the sensitivity of TEC data derived from GNSS stations to Earthquakes, sensitivity of GNSS and LP data at around 500 km high orbit is analyzed here. A similar orbital height can be found in case of many LEO missions equipped at least with GNSS POD receivers, which makes Swarm especially interesting data acquisition platforms.</p><p>The investigation of Swarm data in view of Tsunamis and earthquakes is difficult due to several factors. There are only three satellites, the two of which fly almost together, which gives in fact only two points of the survey. The orbital repetition period is long, which seriously limits the number of comparable observations in terms of the location and time of the day. Finally, the number of large earthquakes and tsunami events in time of Swarm science mission is low, and many Earthquakes do not coincide sufficiently with Swarm passes in time and space. All these factors, however, doesn’t exclude an opportunity of analyzing of Swarm data passes above the earthquakes of magnitude nearby 8, linked with the tsunamis reaching several decimeters.</p><p>Swarm LP data is detrended and analyzed before the earthquakes and also during the earthquakes and resulting tsunami events. The GNSS POD topside TEC from Swarm is analyzed together as a background for LP data. In-situ electron density disturbances occurring during a pass close to the earthquake is compared to selected STEC measurements between LEO and GNSS satellites. Additionally absolute STEC values from selected nearby ground stations are analyzed in order to  find existing correlations for detected disturbances in the electric and magnetic fields. All the observations are sparse in time and space, and therefore, leave some unanswered questions and uncertainties. However, several interesting perturbations over earthquake/tsunami events are observable in both Swarm LP data and GNSS TEC data.</p>

scholarly journals Evidence of gravity waves into the atmosphere during the March 2006 total solar eclipse

2007 ◽  
Vol 7 (18) ◽  
pp. 4943-4951 ◽  
Author(s):  
C. S. Zerefos ◽  
E. Gerasopoulos ◽  
I. Tsagouri ◽  
B. E. Psiloglou ◽  
A. Belehaki ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Electron Density ◽  
Gravity Waves ◽  
Solar Eclipse ◽  
Stratospheric Ozone ◽  
Thermal Fluctuations ◽  
Ozone Layer ◽  
Total Solar Eclipse ◽  
Electron Content ◽  
Total Electron

Abstract. This study aims at providing experimental evidence, to support the hypothesis according to which the movement of the moon's shadow sweeping the ozone layer at supersonic speed, during a solar eclipse, creates gravity waves in the atmosphere. An experiment was conducted to study eclipse induced thermal fluctuations in the ozone layer (via measurements of total ozone column, ozone photolysis rates and UV irradiance), the ionosphere (Ionosonde Total Electron Content – ITEC, peak electron density height – hmF2), and the troposphere (temperature, relative humidity), before, during and after the total solar eclipse of 29 March 2006. We found the existence of eclipse induced dominant oscillations in the parameters related to the ozone layer and the ionosphere, with periods ranging between 30–40 min. Cross-spectrum analyses resulted to statistically significant square coherences between the observed oscillations, strengthening thermal stratospheric ozone forcing as the main mechanism for GWs. Additional support for a source below the ionosphere was provided by the amplitude of the oscillations in the ionospheric electron density, which increased upwards from 160 to 220 km height. Even though similar oscillations were shown in surface temperature and relative humidity data, no clear evidence for tropospheric influence could be derived from this study, due to the modest amplitude of these waves and the manifold rationale inside the boundary layer.

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

2021 ◽  
Author(s):  
Fuqing Huang ◽  
Jiuhou Lei ◽  
Chao Xiong
Keyword(s):  
Electron Density ◽  
Electron Content ◽  
Radio Waves ◽  
Plasma Bubble ◽  
Total Electron ◽  
Middle Latitudes ◽  
Multiple Observations ◽  
Equatorial Plasma Bubbles ◽  
Low Latitudes

<p>Equatorial plasma bubbles (EPBs) are typically ionospheric irregularities that frequently occur at the low latitudes and equatorial regions, which can significantly affect the propagation of radio waves. In this study, we reported a unique strong EPB that happened at middle latitudes over the Asian sector during the quiescent period. The multiple observations including total electron content (TEC) from Beidou geostationary satellites and GPS, ionosondes, in-situ electron density from SWARM and meteor radar are used to explore the characteristic and mechanism of the observed EPB. The unique strong EPB was associated with great nighttime TEC/electron density enhancement at the middle latitudes, which moves toward eastward. The potential physical processes of the observed EPB are also discussed.</p>

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