GPS‐derived ionospheric total electron content response to a solar flare that occurred on 14 July 2000

Abstract

[1] This paper studies the ionospheric response to an X5.7/3B solar flare that occurred at 10:03 UT on 14 July 2000. With Global Positioning System (GPS) observations, temporal evolution of the ionospheric total electron content (TEC) values was obtained within the latitude range of 30°N $ 45°N and the longitude range of 15°E $ 45°E. It was found that dayside TEC values were enhanced during the flare event, which could be as large as 5 TECU (1 TECU = 10 16 /m 2 ) in regions with small solar zenith angles. The enhancement tended to depend on latitude, longitude and the solar zenith angle of the subionospheric point. However, the TEC enhancement derived from the latitude belt between 30°N and 45°N was not symmetrical about either the longitude or the local hour; it was smaller in the local morning than in the afternoon. The TEC enhancement in the Southern Hemisphere seems to be larger than that in the Northern Hemisphere for the same solar zenith angle. This implies that the background levels of the ionosphere and thermosphere had some influence on the TEC enhancement. The temporal variation of TEC shows minor correlative disturbances from 10:15 UT to 10:27 UT when the solar flare was in the maximum phase. It is likely that the minor disturbances resulted from the evolution of flare emission in the EUV domain.

Solar flare detection system based on global positioning system data: First results

“…This implies that the assumption that a solar flare induces a simple abrupt increase of TEC is not correct. In this context, similar conclusions to this flare have been reached by the authors of Zhang et al (2002). Consequently, the typical overionization pattern is not found using the detector based on five states.…”

Modeling the responses of the middle latitude ionosphere to solar flares

“…Recently, global views of solar flare effects of the ionosphere by using the GPS network observations have been achieved (e.g. Afraimovich, 2000;Leonovich et al, 2002;Liu et al, 2004;Tsurutani et al, 2005;Zhang et al, 2002;Zhang and Xiao, 2005). Afraimovich (2000) developed a novel technique to detect global ionospheric effects of solar flares, and effects of two powerful flares of the ionosphere were studied as examples.…”

Solar activity effects of the ionosphere: A brief review

“…Chen et al [89] statistically investigated the X-class intensive flare events during 1996-2003 and found a negative relationship between the TEC increment and solar-terrestrial distance and flare duration. The results of Zhang and Xiao [91][92][93][94] show asymmetry of the absolute TEC increment about local noon; that is, the flare-induced TEC increment is greater in the afternoon than in the morning in summer, and the reverse in winter and during the equinox. Moreover, the response is dependent on the flare location on the solar disc [83,92].…”

“…In recent years, many scientists studied global variations of SITEC during solar flares [86][87][88][89][90][91][92][93][94][95][96][97][98]. Representative findings include (1) that GPS-TEC is very sensitive to solar flares, and can be used to monitor M+-class flares, (2) that the conclusion of no correlation between the TEC increments and solar zenith angles [85] is incorrect, and (3) that a strong response is also registered in the thermospheric density [88].…”