scholarly journals Simultaneous observation of traveling ionospheric disturbances in the Northern and Southern Hemispheres

2009 ◽  
Vol 27 (4) ◽  
pp. 1501-1508 ◽  
Author(s):  
C. E. Valladares ◽  
J. Villalobos ◽  
M. A. Hei ◽  
R. Sheehan ◽  
Su. Basu ◽  
...  
Keyword(s):  
Spectral Characteristics ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Total Electron ◽  
Diurnal Variability ◽  
Gps Receivers ◽  
Traveling Ionospheric Disturbances ◽  
The North ◽  
Northern And Southern Hemispheres

Abstract. Measurements of total electron content (TEC) using 263 GPS receivers located in the North and South America continents are presented to demonstrate the simultaneous existence of traveling ionospheric disturbances (TID) at high, mid, and low latitudes, and in both Northern and Southern Hemispheres. The TID observations pertain to the magnetically disturbed period of 29–30 October 2003 also known as the Halloween storm. The excellent quality of the TEC measurements makes it possible to calculate and remove the diurnal variability of TEC and then estimate the amplitude, wavelength, spectral characteristics of the perturbations, and the approximate velocity of the AGW. On 29 October 2003 between 17:00 and 19:00 UT, there existed a sequence of TEC perturbations (TECP), which were associated with the transit of atmospheric gravity waves (AGW) propagating from both auroral regions toward the geographic equator. A marked difference was found between the northern and southern perturbations. In the Northern Hemisphere, the preferred horizontal wavelength varies between 1500 and 1800 km; the propagation velocity is near 700 m/s and the perturbation amplitude about 1 TEC unit (TECu). South of the geographic equator the wavelength of the TECP is as large as 2700 km, the velocity is about 550 m/s, and the TECP amplitude is 3 TECu. Concurrently with our observations, the Jicamarca digisonde observed virtual height traces that exhibited typical features that are associated with TIDs. Here, it is suggested that differences in the local conductivity between northern and southern auroral ovals create a different Joule heating energy term. The quality of these observations illustrates the merits of GPS receivers to probe the ionosphere and thermosphere.

scholarly journals Statistical study of medium-scale traveling ionospheric disturbances in low-latitude ionosphere using an automatic algorithm

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Pin-Hsuan Cheng ◽  
Charles Lin ◽  
Yuichi Otsuka ◽  
Hanli Liu ◽  
Panthalingal Krishanunni Rajesh ◽  
...  
Keyword(s):  
Climate Model ◽  
Geomagnetic Latitude ◽  
Detection Algorithm ◽  
Support Vector ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Low Latitude ◽  
Total Electron ◽  
Medium Scale ◽  
Traveling Ionospheric Disturbances

AbstractThis study investigates the medium-scale traveling ionospheric disturbances (MSTIDs) statistically at the low-latitude equatorial ionization anomaly (EIA) region in the northern hemisphere. We apply the automatic detection algorithm including the three-dimensional fast Fourier transform (3-D FFT) and support vector machine (SVM) on total electron content (TEC) observations, derived from a network of ground-based global navigation satellite system (GNSS) receivers in Taiwan (14.5° N geomagnetic latitude; 32.5° inclination), to identify MSTID from other waves or irregularity features. The obtained results are analyzed statistically to examine the behavior of low-latitude MSTIDs. Statistical results indicate the following characteristics. First, the southward (equatorward) MSTIDs are observed almost every day during 0800–2100 LT in Spring and Winter. At midnight, southward MSTIDs are more discernible in Summer and majority of them are propagating from Japan to Taiwan. Second, northward (poleward) MSTIDs are more frequently detected during 1200–2100 LT in Spring and Summer with the secondary peak of occurrence between day of year (DOY) 100–140 during 0000–0300 LT. The characteristics of the MSTIDs are interpreted with additional observations from radio occultation (RO) soundings of FORMOSAT-3/COSMIC as well as modeled atmospheric waves from the high-resolution Whole Atmosphere Community Climate Model (WACCM) suggesting that the nighttime MSTIDs in Summer is likely connected to the atmospheric gravity waves (AGWs).

scholarly journals Geomagnetic control of the spectrum of traveling ionospheric disturbances based on data from a global GPS network

2001 ◽  
Vol 19 (7) ◽  
pp. 723-731 ◽  
Author(s):  
E. L. Afraimovich ◽  
E. A. Kosogorov ◽  
O. S. Lesyuta ◽  
I. I. Ushakov ◽  
A. F. Yakovets
Keyword(s):  
Geomagnetic Activity ◽  
Time Derivative ◽  
Power Spectra ◽  
Small Scale ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Geomagnetic Disturbances ◽  
Absolute Level ◽  
Total Electron ◽  
Traveling Ionospheric Disturbances

Abstract. In this paper an attempt is made to verify the hypothesis of the role of geomagnetic disturbances as a factor in determining the intensity of traveling ionospheric disturbances (TIDs). To improve the statistical validity of the data, we have used the method involving a global spatial averaging of disturbance spectra of the total electron content (TEC). To characterize the TID intensity quantitatively, we suggest that a new global index of the degree of disturbance should be used, which is equal to the mean value of the rms variations in TEC within the selected range of spectral periods (of 20– 60 min, in the present case). The analysis has been made for a set of 100 to 300 GPS stations for 10 days with a different level of geomagnetic activity (Dst from 0 to –350 nT; the Kp index from 3 to 9). It was found that power spectra of daytime TEC variations in the range of 20–60 min periods under quiet conditions have a power-law form with the slope index k = –2.5. With an increase in the level of magnetic disturbance, there is an increase in the total intensity of TIDs, with a concurrent kink of the spectrum caused by an increase in oscillation intensity in the range of 20–60 min. The TEC variation amplitude is found to be smaller at night than during the daytime, and the spectrum decreases in slope, which is indicative of a disproportionate increase in the amplitude of the small-scale part of the spectrum. It was found that an increase in the level of geomagnetic activity is accompanied by an increase in the total intensity of TEC; however, it does not correlate with the absolute level of Dst, but rather with the value of the time derivative of Dst (a maximum correlation coefficient reaches –0.94). The delay of the TID response of the order of 2 hours is consistent with the view that TIDs are generated in auroral regions, and propagate equatorward with the velocity of about 300–400 m/s.Key words. Ionosphere (ionospheric disturbances; auroral ionosphere; equatorial ionopshere)

scholarly journals Spectral Asymmetry of Near-Concentric Traveling Ionospheric Disturbances Due to Doppler-Shifted Atmospheric Gravity Waves

2021 ◽  
Vol 8 ◽  
Author(s):  
Irfan Azeem
Keyword(s):  
Gravity Waves ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Neutral Wind ◽  
Atmospheric Gravity Waves ◽  
Total Electron ◽  
Traveling Ionospheric Disturbances ◽  
Gnss Receivers ◽  
Spectral Asymmetry ◽  
Atmospheric Gravity

Atmospheric Gravity Waves (AGWs) excited by meteorological sources are one of the prominent sources of variability in the ionosphere. Partially-concentric Traveling Ionospheric Disturbances (TIDs) associated with AGWs launched by convective storms have been reported in Total Electron Content (TEC) data from distributed networks of Global Navigation Satellite System (GNSS) receivers. In this paper, TEC data from GNSS receivers in the COntiguous United States (CONUS) are presented to examine AGWs in the ionosphere generated by a convective thunderstorm on April 28, 2014 over Mississippi (MS) and Tennessee (TN). Our analysis of the TID perturbations in the TEC data shows zonal asymmetry of the wave frequencies. This spectral asymmetry is examined to determine the effects of the background neutral wind on the intrinsic periods of the underlying AGWs. This work shows that if the relative motion of the TID wavefronts and the background neutral wind is in the opposite direction, the intrinsic periods will decrease and if they both travel in the same direction, the intrinsic periods will increase. Furthermore, our results show that the characteristics of the TIDs observed on April 28, 2014 in the TEC over CONUS are consistent with those of underlying AGWs being excited by a point source, such as a deep convection system.

scholarly journals Climatology of Medium-Scale Traveling Ionospheric Disturbances (MSTIDs) Observed with GPS Networks in the North African Region

2020 ◽  
Author(s):  
Temitope Seun Oluwadare ◽  
Norbert Jakowski ◽  
Cesar E. Valladares ◽  
Andrew Oke-Ovie Akala ◽  
Oladipo E. Abe ◽  
...  
Keyword(s):  
Occurrence Rate ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
North African ◽  
African Region ◽  
Occurrence Time ◽  
Medium Scale ◽  
Traveling Ionospheric Disturbances ◽  
The North ◽  
June Solstice

Abstract We present for the first time the climatology of medium-scale traveling ionospheric disturbances (MSTIDs) by using Global Positioning System (GPS) receiver networks on geomagnetically quiet days (Kp ≤ 3) over the North African region during 2008-2016. The ionospheric Total Electron Content (TEC) were estimated from the dual-frequency GPS measurements, and the TEC perturbations (dTEC) data were derived from the estimated TEC data. We focused on the TEC perturbations (dTEC) associated MSTIDs and statistically analyzed its characteristics, occurrence rate, diurnal and seasonal behavior as well as the interannual dependence. The results show that MSTID is a local and seasonal dependence. The results also show that MSTIDs predominantly propagates towards the South (equatorward). The daytime and nighttime MSTIDs increase with solar activity, and its event period is (12 ≤ period ≤ 53 mins), while the dominant amplitude is (0.08 ≤ amp ≤ ~1.5 dTECU). The MSTIDs propagation velocity is dominantly higher at the daytime than nighttime. The study also shows that the disturbance occurrence time is more frequent within the hours of (1200 - 1600 LT), and (1000 - 1400 LT) in December solstice at daytime for stations located in the Northwest (NW) and Northeast (NE) part of the African region, respectively. While at the nighttime, the MSTIDs also exhibits variability in disturbance occurrence time around (NW: 2100–0200 LT) and (NE: 1900–0200 LT) in June solstice, but get extended to March equinox during solar maximum (2014). The mean phase velocity in daytime MSTIDs is higher than the nighttime in every season, except during June solstice.

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.

Seismic ionospheric disturbances related to Chile-Illapel 2015 earthquake and tsunami observed by Swarm and ground GNSS stations

2021 ◽  
Author(s):  
Wojciech Jarmolowski ◽  
Pawel Wielgosz ◽  
Anna Krypiak-Gregorczyk ◽  
Beata Milanowska ◽  
Roger Haagmans
Keyword(s):  
Spectral Analysis ◽  
Seismic Activity ◽  
Spectral Characteristics ◽  
Precise Orbit Determination ◽  
Spatial Relations ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Total Electron ◽  
Gnss Data ◽  
Along Track

<p>The study investigates Swarm data including in-situ electron density (ED) measured by Langmuir Probes (LP) and total electron content (TEC) from precise orbit determination (POD) GNSS receivers in time of Chile-Illapel earthquake (EQ) and tsunami in 2015. The research is based on the symbiosis of Swarm data, ground GNSS data and seismic records combined with the information on EQs and tsunamis. The FFT-based filtering and short-term Fourier transform (STFT) analysis are used in detection of seismic ionospheric disturbances (SID) in ED from LP and POD TEC data. The classification of the spectral characteristics of disturbing along-track signals is supported by their simultaneous search in ground GNSS observations, which gives an opportunity for the validation of the spectral recognition. Ground GNSS data, due to several tens of satellites and thousands of stations, provide the only full spatiotemporal view on SIDs and enable the inspection of their spatial shapes, spatial relations and speeds. The location of dense ground GNSS networks is however limited to selected places. Swarm and other LEO satellite data, in turn, are globally distributed, but they are dense only along the orbital tracks. Therefore, 1D nature of Swarm along-track observations, fast satellite movement and limited chance for spatiotemporal correlation due to the non-repeating orbits, strongly require spectral analysis for better recognition of the signals. The detection of SIDs from along-track Swarm data is also complicated due to the variety of disturbing signals occurring in the ionosphere, and the spectral analysis is also crucial there. STFT spectral approach to along-track Swarm data gives an opportunity for distinguishing the signals of different origin. The analyses of Swarm data provide interesting observations of ionospheric disturbances not only directly related with the largest EQ events and tsunami, but also occurring during entire periods of enhanced seismic activity and at larger distances from EQ epicenter. The disturbing signals triggered by the largest EQs and tsunami were also observed. However their amplitude in the ionosphere is not always such dominating as the amplitude of some other, associated disturbances on the neighboring days. This difference in scale can suggest that the electron disturbances in the ionosphere are rather more generally related to the crustal motion and seismic activity, than solely correlated with large EQs.</p>

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