scholarly journals Probing the ionosphere by the pulsar B0950+08 with help of RadioAstron ground-space baselines

2019 ◽  
Vol 491 (4) ◽  
pp. 5843-5851
Author(s):  
Vladimir I Zhuravlev ◽  
Yu I Yermolaev ◽  
A S Andrianov
Keyword(s):  
Geomagnetic Storm ◽  
Radio Telescope ◽  
Preliminary Analysis ◽  
Very Long Baseline Interferometry ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Total Electron ◽  
Space Radio Telescope ◽  
Long Baseline ◽  
Ionospheric Total Electron Content

ABSTRACT The ionospheric scattering of pulses emitted by PSR B0950+08 is measured using the 10-mRadioAstron Space Radio Telescope, the 300-m Arecibo Radio Telescope, and the 14 x 25-m Westerbork Synthesis Radio Telescope (WSRT) at a frequency band between 316 and 332 MHz. We analyse this phenomenon based on a simulated model of the phase difference obtained between antennas that are widely separated by nearly 25 Earth diameters. We present a technique for processing and analysing the ionospheric total electron content (TEC) at the ground stations of the ground-space interferometer. This technique allows us to derive almost synchronous half-hour structures of the TEC in the ionosphere at an intercontinental distance between the Arecibo and WSRT stations. We find that the amplitude values of the detected structures are approximately twice as large as the values for the TEC derived in the international reference ionosphere (IRI) project. Furthermore, the values of the TEC outside these structures are almost the same as the corresponding values found by the IRI. According to a preliminary analysis, the detected structures were observed during a geomagnetic storm with a minimum Dst index of ∼75 nT generated by interplanetary disturbances, and may be due to the influence of interplanetary and magnetospheric phenomena on ionospheric disturbances. We show that the Space Very Long Baseline Interferometry provides us with new opportunities to study the TEC, and we demonstrate the capabilities of this instrument to research the ionosphere.

scholarly journals A case study of the large-scale traveling ionospheric disturbances in the East Asian sector during the 2015 St. Patrick’s Day geomagnetic storm

2019 ◽  
Author(s):  
Jing Liu ◽  
Dong-He Zhang ◽  
Anthea J. Coster ◽  
Shun-Rong Zhang ◽  
Guan-Yi Ma ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Large Scale ◽  
East Asian ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
East Side ◽  
Total Electron ◽  
Traveling Ionospheric Disturbances ◽  
Propagation Parameters ◽  
Perturbation Maps

Abstract. This study gives the first observation of the large-scale traveling ionospheric disturbances (LSTIDs) in the East Asian sector during the 2015 St. Patrick’s Day (March 17, 2015) geomagnetic storm. For the first time, 3 dense networks of GPS receivers in China and Japan are combined together to obtain the 2-dimensional (2D) vertical total electron content (VTEC) perturbation maps in a wider longitudinal range than previous works in this region. Results show that a negative LSTID spanning at least 60° in longitude (80° E–140° E) occurs and propagating from high to lower latitudes around 09:40–11:20 UT. It is followed by a positive LSTID which shows a tendency of dissipation starting from the East side. The manifestation of the 2D VTEC perturbation maps is in good agreement with the recordings from 2 high-frequency Doppler shift stations and the iso-frequency lines from 8 ionosondes. Then, the propagation parameters of the LSTIDs are estimated by applying least square fitting methods to the distinct structures in the 2D VTEC perturbation plots. In general, the propagation parameters are observably longitudinal dependent. For example, the propagation direction is almost due southward between 105° E–115° E, while it is slightly South by West/East in the West/East side of this region. This feature is probably related to the regional geomagnetic declination. The mean values of the period, trough velocity (Vt), crest velocity (Vc), and wavelength of the wavelike LSTIDs in the studied longitudinal bands are 74.8 ± 1.4 minutes, 578 ± 16 m/s, 617 ± 23 m/s, and 2691 ± 80 km, respectively. Finally, using the VTEC map data from the Madrigal database of the MIT Haystack Observatory, the characteristics of the ionospheric disturbances over the European sector (30° N–70° N, 10° E–20° E) are also studied. The results are very different from those in the East Asian sector in parameters like the occurrence time, oscillation period, and propagation velocities.

scholarly journals Integrity investigation of global ionospheric TEC maps for high-precision positioning

2021 ◽  
Vol 95 (3) ◽  
Author(s):  
Jiaojiao Zhao ◽  
Manuel Hernández-Pajares ◽  
Zishen Li ◽  
Ningbo Wang ◽  
Hong Yuan
Keyword(s):  
Solar Activity ◽  
Geomagnetic Storm ◽  
Precise Point Positioning ◽  
Electron Content ◽  
International Gnss Service ◽  
Total Electron ◽  
Ionospheric Total Electron Content ◽  
Actual Error ◽  
Minimum Solar Activity ◽  
Global Ionospheric Maps

AbstractAside from the ionospheric total electron content (TEC) information, root-mean-square (RMS) maps are also provided as the standard deviations of the corresponding TEC errors in global ionospheric maps (GIMs). As the RMS maps are commonly used as the accuracy indicator of GIMs to optimize the stochastic model of precise point positioning algorithms, it is of crucial importance to investigate the reliability of RMS maps involved in GIMs of different Ionospheric Associated Analysis Centers (IAACs) of the International GNSS Service (IGS), i.e., the integrity of GIMs. We indirectly analyzed the reliability of RMS maps by comparing the actual error of the differential STEC (dSTEC) with the RMS of the dSTEC derived from the RMS maps. With this method, the integrity of seven rapid IGS GIMs (UQRG, CORG, JPRG, WHRG, EHRG, EMRG, and IGRG) and six final GIMs (UPCG, CODG, JPLG, WHUG, ESAG and IGSG) was examined under the maximum and minimum solar activity conditions as well as the geomagnetic storm period. The results reveal that the reliability of the RMS maps is significantly different for the GIMs from different IAACs. Among these GIMs, the values in the RMS maps of UQRG are large, which can be used as ionospheric protection level, while the RMS values in EHRG and ESAG are significantly lower than the realistic RMS. The rapid and final GIMs from CODE, JPL and WHU provide quite reasonable RMS maps. The bounding performance of RMS maps can be influenced by the location of the stations, while the influence of solar activity and the geomagnetic storm is not obvious.

scholarly journals Emergence of a localized total electron content enhancement during the severe geomagnetic storm of 8 September 2017

2019 ◽  
Vol 37 (2) ◽  
pp. 153-161 ◽  
Author(s):  
Carlos Sotomayor-Beltran ◽  
Laberiano Andrade-Arenas
Keyword(s):  
Statistical Method ◽  
Total Electron Content ◽  
Geomagnetic Storm ◽  
Orbit Determination ◽  
Geomagnetic Storms ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Total Electron ◽  
Equatorial Ionization Anomaly ◽  
The Pacific

Abstract. In this work, the results of the analysis on total electron content (TEC) data before, during and after the geomagnetic storm of 8 September 2017 are reported. One of the responses to geomagnetic storms due to the southern vertical interplanetary magnetic field (Bz) is the enhancement of the electron density in the ionosphere. Vertical TEC (VTEC) from the Center for Orbit determination in Europe (CODE) along with a statistical method were used to identify positive and/or negative ionospheric storms in response to the geomagnetic storm of 8 September 2017. When analyzing the response to the storm of 8 September 2017 it was indeed possible to observe an enhancement of the equatorial ionization anomaly (EIA); however, what was unexpected was the identification of a local TEC enhancement (LTE) to the south of the EIA (∼40∘ S, right over New Zealand and extending towards the southeastern coast of Australia and also eastward towards the Pacific). This was a very transitory LTE that lasted approximately 4 h, starting at ∼ 02:00 UT on 8 September where its maximum VTEC increase was of 241.2 %. Using the same statistical method, comparable LTEs in a similar category geomagnetic storm, the 2015 St. Patrick's Day storm, were looked for. However, for the aforementioned storm no LTEs were identified. As also indicated in a past recent study for a LTE detected during the 15 August 2015 geomagnetic storm, an association between the LTE and the excursion of Bz seen during the 8 September 2017 storm was observed as well. Furthermore, it is very likely that a direct impact of the super-fountain effect along with traveling ionospheric disturbances may be playing an important role in the production of this LTE. Finally, it is indicated that the 8 September 2017 LTE is the second one to be detected since the year 2016.

scholarly journals Observable quality assessment of broadband very long baseline interferometry system

2021 ◽  
Vol 95 (5) ◽  
Author(s):  
Ming H. Xu ◽  
James M. Anderson ◽  
Robert Heinkelmann ◽  
Susanne Lunz ◽  
Harald Schuh ◽  
...  
Keyword(s):  
Group Delay ◽  
Very Long Baseline Interferometry ◽  
Causative Factor ◽  
Measurement Noise ◽  
Global Network ◽  
Electron Content ◽  
Total Electron ◽  
Long Baseline ◽  
Systematic Effects ◽  
Source Structure

AbstractThe next-generation, broadband geodetic very long baseline interferometry system, named VGOS, is developing its global network, and VGOS networks with a small size of 3–7 stations have already made broadband observations from 2017 to 2019. We made quality assessments for two kinds of observables in the 21 VGOS sessions currently available: group delay and differential total electron content ($$\delta $$ δ TEC). Our study reveals that the random measurement noise of VGOS group delays is at the level of less than 2 ps ($$1\,\hbox {ps}\,=\,10^{-12}$$ 1 ps = 10 - 12  s), while the contributions from systematic error sources, mainly source structure related, are at the level of 20 ps. Due to the significant improvement in measurement noise, source structure effects with relatively small magnitudes that are not overwhelming in the S/X VLBI system, for instance 10 ps, are clearly visible in VGOS observations. Another critical error source in VGOS observations is discrete delay jumps, for instance, a systematic offset of about 310 ps or integer multiples of that. The predominant causative factor is found to be related to source structure. The measurement noise level of $$\delta $$ δ TEC observables is about 0.07 TECU, but the systematic effects are five times larger than that. A strong correlation between group delay and $$\delta $$ δ TEC observables is discovered with a trend of 40 ps/TECU for observations with large structure effects; there is a second trend in the range 60–70 ps/TECU when the measurement noise is dominant.

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.

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