Mapping the Impact of Non-Tectonic Forcing mechanisms on GNSS measured Coseismic Ionospheric Perturbations

AbstractGlobal Navigation Satellite System (GNSS) measured Total Electron Content (TEC) is now widely used to study the near and far-field coseismic ionospheric perturbations (CIP). The generation of near field (~500–600 km surrounding an epicenter) CIP is mainly attributed to the coseismic crustal deformation. The azimuthal distribution of near field CIP may contain information on the seismic/tectonic source characteristics of rupture propagation direction and thrust orientations. However, numerous studies cautioned that before deriving the listed source characteristics based on coseismic TEC signatures, the contribution of non-tectonic forcing mechanisms needs to be examined. These mechanisms which are operative at ionospheric altitudes are classified as the i) orientation between the geomagnetic field and tectonically induced atmospheric wave perturbations ii) orientation between the GNSS satellite line of sight (LOS) geometry and coseismic atmospheric wave perturbations and iii) ambient electron density gradients. So far, the combined effects of these mechanisms have not been quantified. We propose a 3D geometrical model, based on acoustic ray tracing in space and time to estimate the combined effects of non-tectonic forcing mechanisms on the manifestations of GNSS measured near field CIP. Further, this model is tested on earthquakes occurring at different latitudes with a view to quickly quantify the collective effects of these mechanisms. We presume that this simple and direct 3D model would induce and enhance a proper perception among the researchers about the tectonic source characteristics derived based on the corresponding ionospheric manifestations.

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Tropospheric and Ionospheric Anomalies Induced by Volcanic and Saharan Dust Events as Part of Geosphere Interaction Phenomena

Geosciences ◽

10.3390/geosciences9040177 ◽

2019 ◽

Vol 9 (4) ◽

pp. 177 ◽

Cited By ~ 2

Author(s):

Valerio Tramutoli ◽

Francesco Marchese ◽

Alfredo Falconieri ◽

Carolina Filizzola ◽

Nicola Genzano ◽

...

Keyword(s):

Chemical Potential ◽

Saharan Dust ◽

Optical Data ◽

Electron Content ◽

Total Electron ◽

Ionospheric Perturbations ◽

Gps Tec ◽

Dust Events ◽

Electro Magnetic ◽

The Impact

In this work, we assessed the possible relation of ionospheric perturbations observed by Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER), Global Positioning System total electron content (GPS TEC), National Oceanic and Atmospheric Administration (NOAA)-derived outgoing longwave-Earth radiation (OLR), and atmospheric chemical potential (ACP) measurements, with volcanic and Saharan dust events identified by ground and satellite-based medium infrared/thermal infrared (MIR/TIR) observations. The results indicated that the Mt. Etna (Italy) volcanic activity of 2006 was probably responsible for the ionospheric perturbations revealed by DEMETER on 4 November and 6 December and by GPS TEC observations on 4 November and 12 December. This activity also affected the OLR (on 26 October; 6 and 23 November; and 2, 6, and 14 December) and ACP (on 31 October–1 November) analyses. Similarly, two massive Saharan dust episodes, detected by Robust Satellite Techniques (RST) using Spinning Enhanced Visible and Infrared Imager (SEVIRI) optical data, probably caused the ionospheric anomalies recorded, based on DEMETER and GPS TEC observations, over the Mediterranean basin in May 2008. The study confirmed the perturbing effects of volcanic and dust events on tropospheric and ionospheric parameters. Further, it demonstrated the advantages of using independent satellite observations to investigate atmospheric phenomena, which may not always be well documented. The impact of this increased detection capacity in reducing false positives, in the framework of a short-term seismic hazard forecast based on the study of ionospheric and tropospheric anomalies, is also addressed.

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Implications of Ionospheric Scintillation for GNSS Users in Northern Europe

Journal of Navigation ◽

10.1017/s0373463305003218 ◽

2005 ◽

Vol 58 (2) ◽

pp. 241-256 ◽

Cited By ~ 45

Author(s):

Marcio Aquino ◽

Terry Moore ◽

Alan Dodson ◽

Sam Waugh ◽

Jock Souter ◽

...

Keyword(s):

Northern Europe ◽

Ionospheric Scintillation ◽

Electron Content ◽

Total Electron ◽

Northern European ◽

Amplitude Fluctuations ◽

The Uk ◽

Time Delay Effect ◽

Electron Density Irregularities ◽

The Impact

Extensive ionospheric scintillation and Total Electron Content (TEC) data were collected by the Institute of Engineering Surveying and Space Geodesy (IESSG) in Northern Europe during years of great impact of the solar maximum on GNSS users (2001–2003). The ionospheric TEC is responsible for range errors due to its time delay effect on transionospheric signals. Electron density irregularities in the ionosphere, occurring frequently during these years, are responsible for (phase and amplitude) fluctuations on GNSS signals, known as ionospheric scintillation. Since June 2001 four GPS Ionospheric Scintillation and TEC Monitor receivers (the NovAtel/AJ Systems GSV4004) have been deployed at stations in the UK and Norway, forming a Northern European network, covering geographic latitudes from 53° to 70° N approximately. These receivers compute and record GPS phase and amplitude scintillation parameters, as well as TEC and TEC variations. The project involved setting up the network and developing automated archiving and data analysis strategies, aiming to study the impact of scintillation on DGPS and EGNOS users, and on different GPS receiver technologies. In order to characterise scintillation and TEC variations over Northern Europe, as well as investigate correlation with geomagnetic activity, long-term statistical analyses were also produced. This paper summarises our findings, providing an overview of the potential implications of ionospheric scintillation for the GNSS user in Northern Europe.

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Total Electron Content (TEC) estimation over Pakistan from local GPS network using spherical harmonics

Annals of Geophysics ◽

10.4401/ag-8433 ◽

2021 ◽

Vol 64 (1) ◽

Author(s):

Maria Mehmood ◽

Sajid Saleem ◽

Renato Filjar ◽

Najam Naqvi ◽

Arslan Ahmed

Keyword(s):

Spherical Harmonics ◽

Orbit Determination ◽

Region Of Interest ◽

Local Model ◽

Small Scale ◽

Electron Content ◽

Total Electron ◽

Gps Network ◽

Spherical Harmonics Expansion ◽

The Impact

Many organizations allow GNSS users to access Global Ionosphere Maps (GIMS). However, the TEC estimates derived from GIMs are of insufficient quality to describe small-scale TEC variations over Pakistan. In this paper, the first local TEC map over Pakistan for the year 2019, derived from a regional GPS network, is presented. Spherical harmonics expansion is employed to estimate TEC with the spatial resolution of latitude 0.2° x longitude 0.2° and temporal resolution of 5 minutes. The impact of changing the degree/order of harmonics is assessed and it is determined that harmonic expansion up to 6 degrees is sufficient for estimating accurate TEC map for the region of interest. We have demonstrated that the TEC maps of Pakistan generated by local model conform better to the GIM by Center of Orbit Determination (CODE) (RMS = 5.83) as compared to International Reference Ionosphere (IRI-2016) (RMS = 7.18). We found that the TEC estimated by the local model shows a better correlation to measured TEC; CODE-GIM overestimated TEC, while IRI-2016 underestimates it. Moreover, it was observed that TEC peaks during noon (1100-0100 LT) and Equinox (April). The residuals of local TEC estimates with respect to TEC obtained from CODE- GIM indicate the inaccuracy of CODE-GIM over the region of Pakistan: highest deviation of TEC from local model with respect to CODE –GIM was observed in April (RMS = 8.73) and minimum in October (RMS = 2.78). We have also analyzed the performance of our maps in geomagnetically disturbed days. The research presented in this paper will contribute towards the ionosphere study over Pakistan, where limited research is available currently.

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Validating the impact of various ionosphere correction on mid to long baselines and point positioning using GPS dual-frequency receivers

Journal of Applied Geodesy ◽

10.1515/jag-2021-0040 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Alaa A. Elghazouly ◽

Mohamed I. Doma ◽

Ahmed A. Sedeek

Keyword(s):

Geomagnetic Storms ◽

Global Navigation Satellite Systems ◽

Electron Content ◽

Assessment Procedure ◽

Vertical Total Electron Content ◽

Dual Frequency ◽

Total Electron ◽

Satellite Systems ◽

Point Positioning ◽

The Impact

Abstract Due to the ionosphere delay, which has become the dominant GPS error source, it is crucial to remove the ionospheric effect before estimating point coordinates. Therefore, different agencies started to generate daily Global Ionosphere Maps (GIMs); the Vertical Total Electron Content (VTEC) values represented in GIMs produced by several providers can be used to remove the ionosphere error from observations. In this research, An analysis will be carried with three sources for VTEC maps produced by the Center for Orbit Determination in Europe (CODE), Regional TEC Mapping (RTM), and the International Reference Ionosphere (IRI). The evaluation is focused on the effects of a specific ionosphere GIM correction on the precise point positioning (PPP) solutions. Two networks were considered. The first network consists of seven Global Navigation Satellite Systems (GNSS) receivers from (IGS) global stations. The selected test days are six days, three of them quiet, and three other days are stormy to check the influence of geomagnetic storms on relative kinematic positioning solutions. The second network is a regional network in Egypt. The results show that the calculated coordinates using the three VTEC map sources are far from each other on stormy days rather than on quiet days. Also, the standard deviation values are large on stormy days compared to those on quiet days. Using CODE and RTM IONEX file produces the most precise coordinates after that the values of IRI. The elimination of ionospheric biases over the estimated lengths of many baselines up to 1000 km has resulted in positive findings, which show the feasibility of the suggested assessment procedure.

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Ionospheric response to magnetar flare: signature of SGR J1550–5418 on coherent ionospheric Doppler radar

Annales Geophysicae ◽

10.5194/angeo-35-345-2017 ◽

2017 ◽

Vol 35 (3) ◽

pp. 345-351 ◽

Cited By ~ 3

Author(s):

Ayman Mahrous

Keyword(s):

Total Electron Content ◽

Large Scale ◽

Doppler Radar ◽

Ionospheric Disturbance ◽

Eastern Mediterranean ◽

Small Scale ◽

Electron Content ◽

Total Electron ◽

Ionospheric Perturbations ◽

Onset Phase

Abstract. This paper presents observational evidence of frequent ionospheric perturbations caused by the magnetar flare of the source SGR J1550–5418, which took place on 22 January 2009. These ionospheric perturbations are observed in the relative change of the total electron content (ΔTEC/Δt) measurements from the coherent ionospheric Doppler radar (CIDR). The CIDR system makes high-precision measurements of the total electron content (TEC) change along ray-paths from ground receivers to low Earth-orbiting (LEO) beacon spacecraft. These measurements can be integrated along the orbital track of the beacon satellite to construct the relative spatial, not temporal, TEC profiles that are useful for determining the large-scale plasma distribution. The observed spatial TEC changes reveal many interesting features of the magnetar signatures in the ionosphere. The onset phase of the magnetar flare was during the CIDR's nighttime satellite passage. The nighttime small-scale perturbations detected by CIDR, with ΔTEC/Δt  ≥  0.05 TECU s−1, over the eastern Mediterranean on 22 January 2009 were synchronized with the onset phase of the magnetar flare and consistent with the emission of hundreds of bursts detected from the source. The maximum daytime large-scale perturbation measured by CIDR over northern Africa and the eastern Mediterranean was detected after ∼ 6 h from the main phase of the magnetar flare, with ΔTEC/Δt  ≤  0.10 TECU s−1. These ionospheric perturbations resembled an unusual poleward traveling ionospheric disturbance (TID) caused by the extraterrestrial source. The TID's estimated virtual velocity is 385.8 m s−1, with ΔTEC/Δt  ≤  0.10 TECU s−1.

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Ionospheric Responses to the June 2015 Geomagnetic Storm from Ground and LEO GNSS Observations

Remote Sensing ◽

10.3390/rs12142200 ◽

2020 ◽

Vol 12 (14) ◽

pp. 2200

Author(s):

Chao Gao ◽

Shuanggen Jin ◽

Liangliang Yuan

Keyword(s):

Geomagnetic Storm ◽

Geomagnetic Storms ◽

Low Earth Orbit ◽

Horizontal Gradient ◽

Electron Content ◽

Vertical Total Electron Content ◽

Total Electron ◽

Leo Satellites ◽

The Impact ◽

Gnss Observations

Geomagnetic storms are extreme space weather events, which have considerable impacts on the ionosphere and power transmission systems. In this paper, the ionospheric responses to the geomagnetic storm on 22 June 2015, are analyzed from ground-based and satellite-based Global Navigation Satellite System (GNSS) observations as well as observational data of digital ionosondes, and the main physical mechanisms of the ionospheric disturbances observed during the geomagnetic storm are discussed. Salient positive and negative storms are observed from vertical total electron content (VTEC) based on ground-based GNSS observations at different stages of the storm. Combining topside observations of Low-Earth-Orbit (LEO) satellites (GRACE and MetOp satellites) with different orbital altitudes and corresponding ground-based observations, the ionospheric responses above and below the orbits are studied during the storm. To obtain VTEC from the slant TEC between Global Positioning System (GPS) and LEO satellites, we employ a multi-layer mapping function, which can effectively reduce the overall error caused by the single-layer geometric assumption where the horizontal gradient of the ionosphere is not considered. The results show that the topside observations of the GRACE satellite with a lower orbit can intuitively detect the impact caused by the fluctuation of the F2 peak height (hmF2). At the same time, the latitude range corresponding to the peak value of the up-looking VTEC on the event day becomes wider, which is the precursor of the Equatorial Ionization Anomaly (EIA). However, no obvious response is observed in the up-looking VTEC from MetOp satellites with higher orbits, which indicates that the VTEC responses to the geomagnetic storm mainly take place below the orbit of MetOp satellites.

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Pre-Earthquake and Coseismic Ionosphere Disturbances of the Mw 6.6 Lushan Earthquake on 20 April 2013 Monitored by CMONOC

Atmosphere ◽

10.3390/atmos10040216 ◽

2019 ◽

Vol 10 (4) ◽

pp. 216 ◽

Cited By ~ 4

Author(s):

Shi ◽

Liu ◽

Guo ◽

Liu ◽

You ◽

...

Keyword(s):

Acoustic Wave ◽

Propagation Velocity ◽

Ionospheric Disturbance ◽

Lower Thermosphere ◽

Propagation Speed ◽

Lushan Earthquake ◽

Electron Content ◽

Terrestrial Environment ◽

Total Electron ◽

The Impact

In order to study the coupling relationship between large earthquakes and the ionosphere, the techniques of ionosphere data acquisition were refined by the Crustal Movement Observation Network of China (CMONOC) to detect the pre-earthquake ionospheric abnormal and coseismic ionospheric disturbances (CID) of the Mw 6.6 Lushan earthquake on 20 April 2013. Based on the regional ionosphere maps (RIMs) derived from the Global Positioning System (GPS) observations of CMONOC, the ionospheric local effects near the epicenter of the Lushan earthquake one month prior to the shock were analyzed. The results show that the total electron content (TEC) anomalies appeared 12–14 (6–8 April), 19 (1 April), and 25–27 (24–26 March) days prior to the Lushan earthquake, which are defined as periods 1, 2, and 3, respectively. Multi-indices including the ring current index (Dst), geomagnetic planetary (Kp) index, wind plasma speed (Vsw) index, F10.7, and solar flares were utilized to represent the solar–terrestrial environment in different scales and eliminate the effects of solar and geomagnetic activities on the ionosphere. After the interference of solar–terrestrial activity and the diurnal variation in the lower thermosphere were excluded, the TEC variations with obvious equatorial ionospheric anomaly (EIA) in period-1 were considered to be related to the Lushan earthquake. We further retrieved precise slant TECs (STECs) near the epicenter to study the coseismic ionospheric disturbance (CID). The results show that there was clear STEC disturbance occurring within half an hour after the Lushan earthquake, and the CID propagation distance was less than the impact radius of the Lushan earthquake (689 km). The shell models with different altitudes were adopted to analyze the propagation speed of the CID. It is found that at the F2-layer with the altitude of 277 km, which had a CID horizontal propagation velocity of 0.84 ± 0.03 km/s, was in accordance with the acoustic wave propagation velocity. The calculated velocity acoustic wave from the epicenter to the ionospheric pierce points of this shell model was about 0.53 ± 0.03km/s, which was also consistent with its actual velocity within the altitude of 0–277 km. Affected by the geomagnetic field, the CID mainly propagated along the southeast direction at the azimuth of 190°, which was almost parallel to the local magnetic line.

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A new model for ionospheric total electron content: the impact of solar flux proxies and indices

10.1002/essoar.10503730.1 ◽

2020 ◽

Author(s):

Larisa P. Goncharenko ◽

Cole A Tamburri ◽

W. Kent Tobiska ◽

Samuel Schonfeld ◽

Phillip C Chamberlin ◽

...

Keyword(s):

Total Electron Content ◽

Solar Flux ◽

Electron Content ◽

Total Electron ◽

New Model ◽

Ionospheric Total Electron Content ◽

The Impact

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Response of the low- to mid-latitude ionosphere to the geomagnetic storm of September 2017

Annales Geophysicae ◽

10.5194/angeo-38-359-2020 ◽

2020 ◽

Vol 38 (2) ◽

pp. 359-372 ◽

Cited By ~ 4

Author(s):

Nadia Imtiaz ◽

Waqar Younas ◽

Majid Khan

Keyword(s):

Geomagnetic Storm ◽

High Speed ◽

Density Ratio ◽

Time Response ◽

Magnetic Observatory ◽

Electron Content ◽

Vertical Total Electron Content ◽

Total Electron ◽

Storm Effects ◽

The Impact

Abstract. We study the impact of the geomagnetic storm of 7–9 September 2017 on the low- to mid-latitude ionosphere. The prominent feature of this solar event is the sequential occurrence of two SYM-H minima with values of −146 and −115 nT on 8 September at 01:08 and 13:56 UT, respectively. The study is based on the analysis of data from the Global Positioning System (GPS) stations and magnetic observatories located at different longitudinal sectors corresponding to the Pacific, Asia, Africa and the Americas during the period 4–14 September 2017. The GPS data are used to derive the global, regional and vertical total electron content (vTEC) in the four selected regions. It is observed that the storm-time response of the vTEC over the Asian and Pacific sectors is earlier than over the African and American sectors. Magnetic observatory data are used to illustrate the variation in the magnetic field particularly, in its horizontal component. The global thermospheric neutral density ratio; i.e., O∕N2 maps obtained from the Global UltraViolet Spectrographic Imager (GUVI) on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite are used to characterize the storm-time response of the thermosphere. These maps exhibit a significant storm-time depletion of the O∕N2 density ratio in the northern middle and lower latitudes over the western Pacific and American sectors as compared to the eastern Pacific, Asian and African sectors. However, the positive storm effects in the O∕N2 ratio can be observed in the low latitudes and equatorial regions. It can be deduced that the storm-time thermospheric and ionospheric responses are correlated. Overall, the positive ionospheric storm effects appear over the dayside sectors which are associated with the ionospheric electric fields and the traveling atmospheric disturbances. It is inferred that a variety of space weather phenomena such as the coronal mass ejection, the high-speed solar wind stream and the solar radio flux are the cause of multiple day enhancements of the vTEC in the low- to mid-latitude ionosphere during the period 4–14 September 2017.

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