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

2020 ◽  
Vol 38 (2) ◽  
pp. 359-372 ◽  
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.

scholarly journals Response of low to mid latitude ionosphere to the Geomagnetic storm of September 2017

2019 ◽  
Author(s):  
Nadia Imtiaz ◽  
Waqar Younas ◽  
Majid Khan
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Storm ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Total Electron ◽  
Storm Effects ◽  
Low Latitudes ◽  
The Impact ◽  
The Magnetic Field ◽  
Magnetic Observatories

Abstract. We study the impact of geomagnetic storm of September 6–9, 2017 on the low-to-mid latitude ionosphere. The prominent feature of this solar event is the sequential occurrence of the two Dst minima of maximum negative values −148 nT and −122 nT on September 8 at 2 UT and 15 UT, respectively. The study is based on analyzing the data from GPS stations and the magnetometer observatories located at different longitudinal sectors such as Asia, Africa and America. The GPS data is used to derive the global, regional and vertical total electron content (TEC) in the selected regions. The data of the magnetic observatories is used to illustrate the variation in the magnetic field particularly, the horizontal component of the magnetic field. It is observed that the storm time response of the TEC over the pre-noon sector (Asia) is earlier than Africa and America. The global thermospheric composition maps by Global Ultraviolet Imager exhibits a storm time variation in the O/N2 ratio. The positive storm effects in the vertical TEC and in the O/N2 ratio occur in the low latitudes/ equatorial regions.

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

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.

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

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.

scholarly journals Evaluation of geomagnetic storm effects on the GPS derived Total Electron Content (TEC)

2015 ◽  
Vol 640 ◽  
pp. 012072 ◽  
Author(s):  
P K Purohit ◽  
Azad A Mansoori ◽  
Parvaiz A Khan ◽  
Roshni Atulkar ◽  
Purushottam Bhawre ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Geomagnetic Storm ◽  
Electron Content ◽  
Total Electron ◽  
Storm Effects

scholarly journals Localized Increment and Decrement in the Total Electron Content of the Ionosphere as a Response to the April 20, 2018, Geomagnetic Storm

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Carlos Sotomayor-Beltran
Keyword(s):  
Total Electron Content ◽  
Geomagnetic Storm ◽  
Longitudinal Section ◽  
Recovery Phase ◽  
Electron Content ◽  
Past Study ◽  
Vertical Total Electron Content ◽  
Total Electron ◽  
Cycle 24 ◽  
Maximum Increment

A moderate geomagnetic storm occurred on April 20, 2018. Using vertical total electron content (VTEC) maps provided by the Center for Orbit Determination in Europe, ionospheric responses to the geomagnetic storm could be identified in generated two-dimensional differential VTEC maps. During the day of the storm the enhancement of the equatorial ionization anomaly (EIA), product of the super-fountain effect was identified. A localized TEC enhancement (LTE) was also observed to the south of the EIA on April 20, 2018. It was also possible to visualize this LTE in a longitudinal section of the EIA as a third crest. The maximum increment of VTEC for the LTE was 204%. This LTE is quite unique because it happened during the expected solar cycle 24 and 25 minimum, and according to a previous study no LTE observation could be done for the last solar two-cycle minimum. The origin of the observed LTE is suggested to be partly product of the super-fountain effect. Finally, a localized TEC decrement (LTD) was observed towards the end of the day, April 20, 2018. Because this LTD consisted in the disappearance of the northern and southern crests of the EIA and this occurred during the recovery phase of the geomagnetic storm, it can be suggested that the LTD origin is due to the westward disturbance electric field. This mechanism was put forward by a past study that also analyzed the responses to a geomagnetic storm (the 2015 St. Patrick’s day storm), being one of the responses the inhibition of both crests of the EIA.

scholarly journals The geomagnetic storm time response of GPS total electron content in the North American sector

2016 ◽  
Vol 121 (2) ◽  
pp. 1744-1759 ◽  
Author(s):  
E. G. Thomas ◽  
J. B. H. Baker ◽  
J. M. Ruohoniemi ◽  
A. J. Coster ◽  
S.‐R. Zhang
Keyword(s):  
Total Electron Content ◽  
Geomagnetic Storm ◽  
North American ◽  
Time Response ◽  
Electron Content ◽  
Total Electron ◽  
The North

scholarly journals Degradation of Kinematic PPP of GNSS Stations in Central Europe Caused by Medium-Scale Traveling Ionospheric Disturbances During the St. Patrick’s Day 2015 Geomagnetic Storm

2020 ◽  
Vol 12 (21) ◽  
pp. 3582
Author(s):  
Mateusz Poniatowski ◽  
Grzegorz Nykiel
Keyword(s):  
Central Europe ◽  
Geomagnetic Storm ◽  
Activity Index ◽  
Satellite System ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Total Electron ◽  
Traveling Ionospheric Disturbances ◽  
Cycle Slips ◽  
The Impact

In solar cycle 24, the strongest geomagnetic storm took place on 17 March 2015, when the geomagnetic activity index was as high as −223 nT. To verify the impact that the storm had on the Global Navigation Satellite System (GNSS)’s positioning accuracy and precision, we used 30-s observations from 15 reference stations located in Central Europe. For each of them, we applied kinematic precise point positioning (PPP) using gLAB software for the day of the storm and, for comparison, for a selected quiet day (13 March 2015). Based on the conducted analyses, we found out that the position root mean square (RMS) values on the day of the geomagnetic storm were significantly high and amounted to several dozen centimeters. The average RMS for the altitude coordinates was 0.58 m between 12:00 and 24:00 (GPS time), and 0.37 and 0.26 m for directions North and East, respectively. The compromised accuracy level was caused by a sudden decrease in the number of satellites used for calculations. This was due to a high number of cycle slips (CSs) detected during this period. The occurrence of these effects was strictly correlated with the appearance of traveling ionospheric disturbances (TIDs). This was proven by analyzing changes in the total electron content (TEC) estimated for each station–satellite pair.

scholarly journals The Influence of Solar X-ray Flares on SAR Meteorology: The Determination of the Wet Component of the Tropospheric Phase Delay and Precipitable Water Vapor

2021 ◽  
Vol 13 (13) ◽  
pp. 2609
Author(s):  
Aleksandra Nina ◽  
Jelena Radović ◽  
Giovanni Nico ◽  
Luka Č. Popović ◽  
Milan Radovanović ◽  
...  
Keyword(s):  
Water Vapor ◽  
Total Electron Content ◽  
Precipitable Water ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Total Electron ◽  
X Ray ◽  
D Region ◽  
The Impact

In this work, we study the impact of high-energy radiation induced by solar X-ray flares on the determination of the temporal change in precipitable water vapor (ΔPWV) as estimated using the synthetic aperture radar (SAR) meteorology technique. As recent research shows, this radiation can significantly affect the ionospheric D-region and induces errors in the estimation of the total electron content (TEC) by the applied models. Consequently, these errors are reflected in the determination of the phase delay and in many different types of measurements and models, including calculations of meteorological parameters based on SAR observations. The goal of this study is to quantify the impact of solar X-ray flares on the estimation of ΔPWV and provide an estimate of errors induced if the vertical total electron content (VTEC) is obtained by single layer models (SLM) or multiple layer models (MLM) (these models do not include ionosphere properties below the altitude of 90 km as input parameters and cannot provide information about local disturbances in the D-region). The performed analysis is based on a known procedure for the determination of the D-region electron density (and, consequently, the vertical total electron content in the D-region (VTECD)) using ionospheric observations of very low frequency (VLF) radio waves. The main result indicates that if the D-region, perturbed by medium-sized and intense X-ray flares, is not modeled, errors occur in the determination of ΔPWV. This study emphasizes the need for improved MLMs for the estimation of the TEC, including observational data at D-region altitudes during medium-sized and intense X-ray flare events.

scholarly journals Large ionospheric disturbances during a minor geomagnetic storm on June 23, 2000

2012 ◽  
Vol 55 (2) ◽  
Author(s):  
Zheng Li ◽  
Fengsi Wei ◽  
Xueshang Feng ◽  
Jianpeng Guo ◽  
Barbara A Emery ◽  
...  
Keyword(s):  
Solar Wind ◽  
Geomagnetic Storm ◽  
Northern Hemisphere ◽  
Global Positioning System ◽  
Energy Input ◽  
Electron Content ◽  
Positioning System ◽  
Total Electron ◽  
Storm Effects ◽  
Global Positioning

<p>We investigate the variations in the ionosphere during a small geomagnetic storm on June 23, 2000, using the total electron content of the Jet Propulsion Laboratory global positioning system, and the ionospheric critical frequency. Large and long-lasting reductions in the daytime electron density were observed at mid-latitudes in the northern hemisphere by ionosondes. These reductions reached 30% to 40% compared to the 27-day median value. At the same time, a transformation from similar large positive storm effects to negative storm effects was observed in the northern hemisphere by the global positioning system receivers. The geomagnetic disturbance was very weak from June 23-25, 2000, as the SYM-H index was &gt;−40 nT and ASY-H was &lt;90 nT. Of note, during this case there were neither long-lasting southward IMF Bz nor strong positive IMF By components, where a large positive IMF By might be the main reason for ionospheric storms during minor geomagnetic disturbances [Goncharenko et al. 2006]. We confirm a 13-h enhanced energy input from the disturbed solar wind by calculation of the Borovsky, Akasofu and Newell coupling functions, the global auroral precipitation, and the Joule heating. We suggest this enhanced energy input as the main cause of these intense ionospheric storms, although the maximum of the energy input was not large. In addition, we propose that the Newell coupling function might be more suitable for reflecting the energy transfer from the disturbed solar wind to the magnetosphere under weak geomagnetic activity.</p>

Regional Ionosphere VTEC Modelling and Application for Single-Frequency Positioning in the Western Balkans

2020 ◽  
Author(s):  
Randa Natras ◽  
Andreas Goss
Keyword(s):  
Linear Combination ◽  
Geomagnetic Storm ◽  
Single Frequency ◽  
High Solar Activity ◽  
Model Parameters ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Dual Frequency ◽  
Western Balkans ◽  
Total Electron

&lt;p&gt;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&amp;#8217;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.&lt;/p&gt;&lt;p&gt;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 40&amp;#8304; N to 47&amp;#8304; N and 13&amp;#8304; E to 23&amp;#8304; 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&lt;/p&gt;&lt;p&gt;The developed ionosphere IONO_WB model is tested for periods of the solar maximum (March 2014) and the St. Patrick&amp;#180;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.&lt;/p&gt;

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