scholarly journals Ionospheric Response over Nepal during the 26 December 2019 Solar Eclipse

2021 ◽  
Vol 7 (1) ◽  
pp. 25-30
Author(s):  
A. Silwal ◽  
S. P. Gautam ◽  
N. P. Chapagain ◽  
M. Karki ◽  
P. Poudel ◽  
...  
Keyword(s):  
Solar Eclipse ◽  
Satellite System ◽  
Electron Content ◽  
Total Electron ◽  
North West ◽  
North East ◽  
Apparent Variation ◽  
Gnss Measurements ◽  
Global Navigation Satellite ◽  
Annular Solar Eclipse

On 26th December 2019, during morning hours, an annular solar eclipse having a magnitude of 0.96 with a 118 km wide antumbra occurred and lasted for 3 minutes and 40 seconds at the point of maximum eclipse. The partial eclipse was visible in most of Asia, parts of North/East Africa, and North/West Australia. In the context of Nepal, only the partial eclipse was visible from ~ 8:34 LT (02:51 UT) and ended at ~ 11:40 LT (05:55 UT). It was 2 hours 47 mins and 54 secs long with the maximum visible eclipse time at ~ 10:01 LT (04:16 UT). Our study is based on Global Navigation Satellite System (GNSS) measurements from a widely distributed Global Positioning System (GPS) network over different places of Nepal on the day of the eclipse, a day before, and a day after the eclipse. We investigated the ionospheric behavior through the changes in Total Electron Content (TEC) during the partial eclipse by using the data archived at the five different GPS stations of Nepal. The result reveals that there is significant depletion of TEC, in some cases greater than 20% compared to other normal days. Observing the values of TEC before, during, and after the event, our study showed an apparent variation during the time of the eclipse, which agrees with previous studies on ionospheric responses to the eclipse as well as theoretical assumptions.

scholarly journals A multi-instrumental and modelling analysis of the ionospheric responses to the solar eclipse of December 14, 2020, over the Brazilian region

2021 ◽  
Author(s):  
Laysa Cristina Araujo Resende ◽  
Yajun Zhu ◽  
Clezio Marcos Denardini ◽  
Sony Su Chen ◽  
Ronan Arraes Jardim Chagas ◽  
...  
Keyword(s):  
Solar Eclipse ◽  
Satellite System ◽  
Electron Content ◽  
Electronic Density ◽  
Total Electron ◽  
Density Reduction ◽  
Modelling Analysis ◽  
E Region ◽  
South Of Brazil ◽  
Global Navigation Satellite

Abstract. This work presents an analysis of the ionospheric responses to the solar eclipse that occurred on December 14, 2020, over the Brazilian sector. This event partially covers the south of Brazil, providing an excellent opportunity to study the modifications in the peculiarities that occur in this sector, as the Equatorial Ionization Anomaly (EIA). Therefore, we used the Digisonde data available in this period for two sites, Campo Grande (CG, 20.47° S, 54.60° W, dip ∼23° S) and Cachoeira Paulista (CXP, 22.70° S, 45.01° W, dip ∼35° S), assessing the E, and F regions, and Es layer behaviors. Additionally, a numerical model (MIRE, Portuguese acronym for E Region Ionospheric Model) is used to analyze the E layer dynamics modification around these times. The results show the F1 region disappearance and an apparent electronic density reduction in the E region during the solar eclipse. We also analyzed the total electron content (TEC) maps from the Global Navigation Satellite System (GNSS) that indicate a weakness in the EIA. On the other hand, we observe the rise of the Es layer electron density, which is related to the gravity waves strengthened during solar eclipse events. Finally, our results lead to a better understanding of the restructuring mechanisms in the ionosphere at low latitudes during the solar eclipse events, even though they only partially reached the studied regions.

scholarly journals Investigation of Pre-Earthquake Ionospheric and Atmospheric Disturbances for Three Large Earthquakes in Mexico

Geosciences ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 16
Author(s):  
Christina Oikonomou ◽  
Haris Haralambous ◽  
Sergey Pulinets ◽  
Aakriti Khadka ◽  
Shukra R. Paudel ◽  
...  
Keyword(s):  
Chemical Potential ◽  
Atmospheric Model ◽  
Satellite System ◽  
Seismic Events ◽  
Electron Content ◽  
Total Electron ◽  
Atmospheric Disturbances ◽  
Global Ionospheric Maps ◽  
Global Navigation Satellite ◽  
Large Earthquakes

The purpose of the present study is to investigate simultaneously pre-earthquake ionospheric and atmospheric disturbances by the application of different methodologies, with the ultimate aim to detect their possible link with the impending seismic event. Three large earthquakes in Mexico are selected (8.2 Mw, 7.1 Mw and 6.6 Mw during 8 and 19 September 2017 and 21 January 2016 respectively), while ionospheric variations during the entire year 2017 prior to 37 earthquakes are also examined. In particular, Total Electron Content (TEC) retrieved from Global Navigation Satellite System (GNSS) networks and Atmospheric Chemical Potential (ACP) variations extracted from an atmospheric model are analyzed by performing statistical and spectral analysis on TEC measurements with the aid of Global Ionospheric Maps (GIMs), Ionospheric Precursor Mask (IPM) methodology and time series and regional maps of ACP. It is found that both large and short scale ionospheric anomalies occurring from few hours to a few days prior to the seismic events may be linked to the forthcoming events and most of them are nearly concurrent with atmospheric anomalies happening during the same day. This analysis also highlights that even in low-latitude areas it is possible to discern pre-earthquake ionospheric disturbances possibly linked with the imminent seismic events.

scholarly journals Characterization of multi-scale ionospheric irregularities using ground-based and space-based GNSS observations

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
YuXiang Peng ◽  
Wayne A Scales ◽  
Michael D Hartinger ◽  
Zhonghua Xu ◽  
Shane Coyle
Keyword(s):  
Formation Flying ◽  
Satellite System ◽  
Ionospheric Irregularities ◽  
Mission Design ◽  
Electron Content ◽  
Total Electron ◽  
Spatial And Temporal Scales ◽  
Multi Scale ◽  
Global Navigation Satellite ◽  
Gnss Observations

AbstractIonospheric irregularities can adversely affect the performance of Global Navigation Satellite System (GNSS). However, this opens the possibility of using GNSS as an effective ionospheric remote sensing tool. Despite ionospheric monitoring has been undertaken for decades, these irregularities in multiple spatial and temporal scales are still not fully understood. This paper reviews Virginia Tech’s recent studies on multi-scale ionospheric irregularities using ground-based and space-based GNSS observations. First, the relevant background of ionospheric irregularities and their impact on GNSS signals is reviewed. Next, three topics of ground-based observations of ionospheric irregularities for which GNSS and other ground-based techniques are used simultaneously are reviewed. Both passive and active measurements in high-latitude regions are covered. Modelling and observations in mid-latitude regions are considered as well. Emphasis is placed on the increased capability of assessing the multi-scale nature of ionospheric irregularities using other traditional techniques (e.g., radar, magnetometer, high frequency receivers) as well as GNSS observations (e.g., Total-Electron-Content or TEC, scintillation). Besides ground-based observations, recent advances in GNSS space-based ionospheric measurements are briefly reviewed. Finally, a new space-based ionospheric observation technique using GNSS-based spacecraft formation flying and a differential TEC method is demonstrated using the newly developed Virginia Tech Formation Flying Testbed (VTFFTB). Based on multi-constellation multi-band GNSS, the VTFFTB has been developed into a hardware-in-the-loop simulation testbed with external high-fidelity global ionospheric model(s) for 3-satellite formation flying, which can potentially be used for new multi-scale ionospheric measurement mission design.

scholarly journals Investigation of GIM-TEC disturbances before M ≥ 6.0 inland earthquakes during 2003–2017

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Fuying Zhu ◽  
Yingchun Jiang
Keyword(s):  
Rapid Development ◽  
Science Research ◽  
Satellite System ◽  
Statistical Investigation ◽  
Electron Content ◽  
Total Electron ◽  
Spatial And Temporal Distributions ◽  
Before And After ◽  
Global Ionosphere Map ◽  
Global Navigation Satellite

Abstract With the rapid development of the Global Navigation Satellite System (GNSS) and its wide applications to atmospheric science research, the global ionosphere map (GIM) total electron content (TEC) data are extensively used as a potential tool to detect ionospheric disturbances related to seismic activity and they are frequently used to statistically study the relation between the ionosphere and earthquakes (EQs). Indeed, due to the distribution of ground based GPS receivers is very sparse or absent in large areas of ocean, the GIM-TEC data over oceans are results of interpolation between stations and extrapolation in both space and time, and therefore, they are not suitable for studying the marine EQs. In this paper, based on the GIM-TEC data, a statistical investigation of ionospheric TEC variations of 15 days before and after the 276 M ≥ 6.0 inland EQs is undertaken. After eliminating the interference of geomagnetic activities, the spatial and temporal distributions of the ionospheric TEC disturbances before and after the EQs are investigated and compared. There are no particularly distinct features in the time distribution of the ionospheric TEC disturbances before the inland EQs. However, there are some differences in the spatial distribution, and the biggest difference is precisely in the epicenter area. On the other hand, the occurrence rates of ionospheric TEC disturbances within 5 days before the EQs are overall higher than those after EQs, in addition both of them slightly increase with the earthquake magnitude. These results suggest that the anomalous variations of the GIM-TEC before the EQs might be related to the seismic activities.

scholarly journals Methods of detection of changes in the distribution of observed statistics of time derivatives of the total electron content because of cycle slips in navigation satellite’s signals

2019 ◽  
Vol 30 ◽  
pp. 15007
Author(s):  
George Minasyan ◽  
Ivan Nesterov ◽  
Yaroslav Ilyushin
Keyword(s):  
Total Electron Content ◽  
Satellite System ◽  
Electron Content ◽  
Total Electron ◽  
Cycle Slips ◽  
Phase Data ◽  
Total Electronic Content ◽  
Global Navigation Satellite ◽  
Electronic Content ◽  
Derivatives Of

Based on the analysis of the phase data of the global navigation satellite system, distributions of time derivatives of the L1 phase frequency and the total electronic content are obtained. The change in the distributions of observed statistics of time derivatives of the total electron content was analyzed, because there are cycle slips in signals of navigation satellites. According to the analysis of the statistics of the phase of signals, an assumption about the physical and technical reasons for phase failures was made. The correlation between time derivatives of the phase signals and the total electron content has been obtained, despite the apparent dependence of the latter on the phase of the signal. This ratio showed that neither direct nor inverse dependence of the change in the distribution of time derivatives in both of quantities was found.

scholarly journals Ionospheric effects on the F region during the sunrise for the annular solar eclipse over Taiwan on 21 May 2012

2013 ◽  
Vol 31 (11) ◽  
pp. 1891-1898 ◽  
Author(s):  
Y. J. Chuo
Keyword(s):  
Solar Eclipse ◽  
Peak Height ◽  
Scale Height ◽  
Rate Of Change ◽  
Slab Thickness ◽  
Electron Content ◽  
Total Electron ◽  
F Region ◽  
Northern Pacific ◽  
Annular Solar Eclipse

Abstract. On 21 May 2012 (20:56, Universal Time; UT, on 20 May), an annular solar eclipse occurred, beginning at sunrise over southeast China and moving through Japan, sweeping across the northern Pacific Ocean, and completing its passage over the western United States at sunset on 20 May 2012 (02:49 UT, 21 May). We investigated the eclipse area in Taiwan, using an ionosonde and global positioning system (GPS) satellite measurements. The measurements of foF2, hmF2, bottomside scale height around the peak height (Hm), and slab thickness (B0) were collected at the ionosonde station at Chung-Li Observatory. In addition, we calculated the total electron content (TEC) to study the differences inside and outside the eclipse area, using 3 receivers located at Marzhu (denoted as MATZ), Hsinchu (TNML), and Henchun (HENC). The results showed that the foF2 values gradually decreased when the annularity began and reached a minimum level of approximately 2.0 MHz at 06:30 LT. The hmF2 immediately decreased and then increased during the annular eclipse period. The TEC variations also appeared to deplete in the path of the eclipse and opposite the outside passing area. Further, the rate of change of the TEC values (dTEC / dt measured for 15 min) was examined to study the wave-like fluctuations. The scale height near the F2 layer peak height (Hm) also decreased and then increased during the eclipse period. To address the effects of the annular eclipse in the topside and bottomside ionosphere, this study provides a discussion of the variations between the topside and bottomside ionospheric parameters during the eclipse period.

scholarly journals Ionospheric corrections tailored to the Galileo High Accuracy Service

2021 ◽  
Vol 95 (12) ◽  
Author(s):  
A. Rovira-Garcia ◽  
C. C. Timoté ◽  
J. M. Juan ◽  
J. Sanz ◽  
G. González-Casado ◽  
...  
Keyword(s):  
Satellite Orbit ◽  
Satellite System ◽  
High Accuracy ◽  
Integer Ambiguity ◽  
Electron Content ◽  
Confidence Bounds ◽  
Total Electron ◽  
Phase Measurements ◽  
Model Geometry ◽  
Global Navigation Satellite

AbstractThe Galileo High Accuracy Service (HAS) is a new capability of the European Global Navigation Satellite System that is currently under development. The Galileo HAS will start providing satellite orbit and clock corrections (i.e. non-dispersive effects) and soon it will also correct dispersive effects such as inter-frequency biases and, in its full capability, ionospheric delay. We analyse here an ionospheric correction system based on the fast precise point positioning (Fast-PPP) and its potential application to the Galileo HAS. The aim of this contribution is to present some recent upgrades to the Fast-PPP model, with the emphasis on the model geometry and the data used. The results show the benefits of integer ambiguity resolution to obtain unambiguous carrier phase measurements as input to compute the Fast-PPP model. Seven permanent stations are used to assess the errors of the Fast-PPP ionospheric corrections, with baseline distances ranging from 100 to 1000 km from the reference receivers used to compute the Fast-PPP corrections. The 99% of the GPS and Galileo errors in well-sounded areas and in mid-latitude stations are below one total electron content unit. In addition, large errors are bounded by the error prediction of the Fast-PPP model, in the form of the variance of the estimation of the ionospheric corrections. Therefore, we conclude that Fast-PPP is able to provide ionospheric corrections with the required ionospheric accuracy, and realistic confidence bounds, for the Galileo HAS.

scholarly journals MONITORING OF IONOSPHERIC SCINTILLATION PHENOMENA USING SYNTHETIC APERTURE RADAR (SAR)

2018 ◽  
Vol IV-5 ◽  
pp. 331-337
Author(s):  
S. Mohanty ◽  
C. Carrano ◽  
G. Singh
Keyword(s):  
Satellite System ◽  
Synthetic Aperture ◽  
Ionospheric Scintillation ◽  
Electron Content ◽  
Data Sets ◽  
Low Frequencies ◽  
Total Electron ◽  
Gnss Receiver ◽  
Synthetic Aperture Radars ◽  
Global Navigation Satellite

<p><strong>Abstract.</strong> The applications of synthetic aperture radars (SAR) have increased manifold in the past decade, which includes numerous Earth observation applications such as agriculture, forestry, disaster monitoring cryospheric- and atmospheric- studies. Among them, the potential of SAR for ionospheric studies is gaining importance. The susceptibility of SAR to space weather dynamics, and ionosphere in particular, comes at low frequencies of L- and P-bands. This paper discusses one such scintillation event that was observed by L-band Advanced Land Observation Satellite (ALOS)-2 Phased Array L-type SAR (PALSAR) over southern India on March 23, 2015. The sensors also acquired data sets on four other days on which the ionosphere was quiet. Ionospheric parameter measurements of total electron content (TEC) and amplitude scintillation (S<sub>4</sub>) index from ground-based Global Navigation Satellite System (GNSS) receiver at Tirunelveli was used to establish the ionospheric conditions on the days of SAR acquisition as well as to corroborate the S<sub>4</sub> estimated from SAR. Multi-temporal ALOS-2 data sets were utilized to calculate S<sub>4</sub> from two separate methods and the results have a good agreement with GNSS receiver measurements. This highlights the potential of SAR as an alternate technique of monitoring ionospheric scintillations that can be utilized as complementary to the highly accurate and dedicated measurements from the GNSS networks.</p>

A New Approach to Monitoring the Interplanetary Shock Induced Pulse: TEC Measurements by the GNSS Receiver Network

2020 ◽  
Author(s):  
Xingran Chen ◽  
Quanhan Li ◽  
Qiugang Zong ◽  
Yongqiang Hao
Keyword(s):  
Propagation Speed ◽  
Interplanetary Shock ◽  
Satellite System ◽  
Wave Form ◽  
Electron Content ◽  
Shock Pulse ◽  
Total Electron ◽  
New Approach ◽  
Gnss Receivers ◽  
Global Navigation Satellite

&lt;p&gt;We revisit the typical interplanetary shock event on November 7, 2004, with high resolution total electron content (TEC) measurements obtained by the distributed Global Navigation Satellite System (GNSS) receivers. TEC impulses were observed after the IP shock impinged on the dayside agnetosphere at ~18:27 UT. In view of the similarity of the wave form and the time-delay characteristics, the TEC impulses were regarded as responses to the IP shock, despite the small amplitude (in the order of 0.4 TECU). Particularly, the peak of the TEC impulse was first observed by the receivers located around 120&amp;#176;W geographic longitude (corresponding to noon magnetic local time), while receivers at both sides recorded the impulse sequentially afterwards. From the timedelay of the TEC impulse, we derive the propagation velocity of the shock induced pulse. The angular velocity of the pulse is estimated to be ~2 degree per second, which is in the same order as the propagation speed of a typical shock pulse in the magnetosphere. Our results present global observational features of the shock pulse and provide new aspects to understand the ionospheric-magnetospheric dynamics in response to IP shocks.&lt;/p&gt;

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