Variation of ionospheric total electron content in Taiwan region of the equatorial anomaly from 1994 to 2003

Autor: Chin-Chun Wu, Kan Liou, C.-L. Tseng, Shao-Ju Shan
Rok vydání: 2008
Předmět:
Zdroj: Advances in Space Research. 41:611-616
ISSN: 0273-1177
Popis: The ionospheric total electron content (TEC) in the northern hemispheric equatorial ionospheric anomaly (EIA) region is studied by analyzing dual-frequency signals of the Global Position System (GPS) acquired from a chain of nine observational sites clustered around Taiwan (21.9–26.2°N, 118.4–112.6°E). In this study, we present results from a statistical study of seasonal and geomagnetic effects on the EIA during solar cycle 23: 1994–2003. It is found that TEC at equatorial anomaly crests yield their maximum values during the vernal and autumnal months and their minimum values during the summer (except 1998). Using monthly averaged I c (magnitude of TEC at the northern anomaly crest), semi-annual variations is seen clearly with two maxima occurring in both spring and autumn. In addition, I c is found to be greater in winter than in summer. Statistically monthly values of I c were poorly correlated with the monthly Dst index ( r = −0.22) but were well correlated with the solar emission F 10.7 index ( r = 0.87) for the entire database for the period during 1994–2003. In contrast, monthly values of I c were correlated better with Dst ( r ⩾ 0.72) than with F 10.7 ( r ⩽ 0.56) in every year during the low solar activity period (1994–1997). It suggests that the effect of solar activity on I c is a longer term (years), whereas the effect of geomagnetic activity on I c is a shorter term (months).
Databáze: OpenAIRE
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