scholarly journals Association of Total Electron Content (TEC) and foF2 variations with earthquake events at the anomaly crest region

2009 ◽  
Vol 47 (1) ◽  
Author(s):  
M. Devi ◽  
A. K. Barbara ◽  
A. Depueva
Keyword(s):  
Electric Field ◽  
Total Electron Content ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Total Electron ◽  
Methods And Techniques ◽  
Radio Beacon

The paper attempts to identify ionospheric parameters in association with earthquake at anomaly crest station through VHF Radio Beacon data and ground based ionosonde measurements while the Total Electron Content(TEC) parameters from RB observations are based mainly on data taken over Guwahati (26.2°N, 91.75° E), foF2 data used in the analysis were collected at Ahmadabad (23.01°N, 72.36°E). The paper describes methods and techniques adopted to examine modifications on these parameters if any, due to earthquake preparatory processes at equatorial anomaly crest stations. The mechanism of inducement of density changes in the ionosphere is sought through the generation of strong fountain effect possibly by the development of electric field during the earthquake preparatory process.

scholarly journals Responses of equatorial anomaly to the October-November 2003 superstorms

2005 ◽  
Vol 23 (3) ◽  
pp. 693-706 ◽  
Author(s):  
B. Zhao ◽  
W. Wan ◽  
L. Liu
Keyword(s):  
Electric Field ◽  
Current Theory ◽  
Peak Height ◽  
Shielding Effect ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Total Electron ◽  
Prompt Penetration Electric Field ◽  
Autumnal Equinox ◽  
American Region

Abstract. The responses of Equatorial Ionization Anomaly (EIA) to the superstorms of October-November 2003 were investigated using the total electron content (TEC) measured with global positioning system (GPS) receivers in China, Southeast Asia, Australian (CSAA), and the American regions. Enhanced EIA was seen to be correlated with the southward turning of the interplanetary magnetic field Bz. In both the CSAA and American regions, EIA was intensified, corresponding to a large increase in the F-layer peak height (hmF2) measured by ionosonde and digisonde at middle and equatorial latitudes. However, the enhanced EIA was shown to be more significant during the daytime in the American region, which was associated with a series of large substorms when Bz was stable southward. The prompt penetration electric field and the wind disturbances dynamo electric field are suggested to be responsible for this observation according to current theory, although some features cannot be totally decipherable. Both the ionogram and magnetometer data show the existence of a weak shielding effect whose effect still needs further study. A clear asymmetric ionospheric response was shown in our TEC observations, even though it was only one month after autumnal equinox. The southern EIA crest was totally obliterated on 29 and 30 October in the CSAA region and on 31 October in the American region. Ion temperatures from the Defense Meteorological Satellite Program (DMSP) spacecraft revealed that the unequal energy injection at the polar region might be the reason for this effect. It is concluded that different physical processes have varying degrees of importance on the evolution of EIA in the CSAA and American regions.

Global distribution of persistence of total electron content anomaly

2020 ◽  
Author(s):  
Yang-Yi Sun ◽  
Chieh-Hong Chen ◽  
Jann-Yenq Liu ◽  
Tsung-Yu Wu
Keyword(s):  
Electric Field ◽  
Total Electron Content ◽  
Electron Content ◽  
Neutral Wind ◽  
Large Area ◽  
Atmospheric Gravity Wave ◽  
Total Electron ◽  
Ionospheric Plasma Density ◽  
Gps Products ◽  
Ionospheric Electric Field

<p>Solar activities can disturb the ionosphere globally and induce ionospheric weather phenomena that transit rapidly through a large area. By contrast, sometimes the ionospheric plasma density can remain high or low over a certain location for a few days, which are difficult to be attributed to solar activities. This study shows the location preference of the positive and negative total electron content (TEC) anomalies persisting continuously longer than 24 hours (cross the two terminators) at middle and low latitudes (within ±60ºN geomagnetic latitudes). The TEC is obtained from the global ionospheric map (GIM) of the Center for Orbit Determination in Europe (CODE) (ftp://cddis.gsfc.nasa.gov/pub/gps/products/ionex) under the geomagnetic quiet condition of Kp ≤ 3o during the period of 2005–2018. There are a few (less than 4%) TEC anomalies that can persist over 24 hours. The persistence of the positive TEC anomaly along the ring of fire on the western edge of the Pacific Ocean. The high persistence of the TEC anomalies at midlatitudes suggests that thermospheric neutral wind contributes to the anomaly formation. The temporal and spatial anomalies of the ionospheric electric field, atmospheric electric field (flash), atmospheric gravity wave, and neutral wind over the ring of fire should be further examined for explaining whether the persistence of the TEC anomalies associates with lithospheric activities.</p>

scholarly journals Observations in equatorial anomaly region of total electron content enhancements and depletions

2005 ◽  
Vol 23 (7) ◽  
pp. 2449-2456 ◽  
Author(s):  
N. Dashora ◽  
R. Pandey
Keyword(s):  
Total Electron Content ◽  
Scintillation Index ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Low Latitude ◽  
Total Electron ◽  
First Results ◽  
Spread F ◽  
New Feature ◽  
Low Latitude Ionosphere

Abstract. A GSV 4004A GPS receiver has been operational near the crest of the equatorial anomaly at Udaipur, India for some time now. The receiver provides the line-of-sight total electron content (TEC), the phase and amplitude scintillation index, σφ and S4, respectively. This paper presents the first results on the nighttime TEC depletions associated with the equatorial spread F in the Indian zone. The TEC depletions are found to be very well correlated with the increased S4 index. A new feature of low-latitude TEC is also reported, concerning the observation of isolated and localized TEC enhancements in the nighttime low-latitude ionosphere. The TEC enhancements are not correlated with the S4 index. The TEC enhancements have also been observed along with the TEC depletions. The TEC enhancements have been interpreted as the manifestation of the plasma density enhancements reported by Le et al. (2003). Keywords. Ionosphere (Equatorial ionosphere; Ionospheric irregularities)

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