Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers
Abstract |
We study solar wind\textendashionosphere coupling through the late declining phase/solar minimum and geomagnetic minimum phases during the last solar cycle (SC23) \textendash 2008 and 2009. This interval was characterized by sequences of high-speed solar wind streams (HSSs). The concomitant geomagnetic response was moderate geomagnetic storms and high-intensity, long-duration continuous auroral activity (HILDCAA) events. The JPL Global Ionospheric Map (GIM) software and the GPS total electron content (TEC) database were used to calculate the vertical TEC (VTEC) and estimate daily averaged values in separate latitude and local time ranges. Our results show distinct low- and mid-latitude VTEC responses to HSSs during this interval, with the low-latitude daytime daily averaged values increasing by up to 33 TECU (annual average of ~20 TECU) near local noon (12:00 to 14:00 LT) in 2008. In 2009 during the minimum geomagnetic activity (MGA) interval, the response to HSSs was a maximum of ~30 TECU increases with a slightly lower average value than in 2008. There was a weak nighttime ionospheric response to the HSSs. A well-studied solar cycle declining phase interval, 10\textendash22 October 2003, was analyzed for comparative purposes, with daytime low-latitude VTEC peak values of up to ~58 TECU (event average of ~55 TECU). The ionospheric VTEC changes during 2008\textendash2009 were similar but ~60\% less intense on average. There is an evidence of correlations of filtered daily averaged VTEC data with Ap index and solar wind speed. |
Year of Publication |
2013
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Journal |
Annales Geophysicae
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Volume |
31
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Number of Pages |
263-276
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Date Published |
01/2013
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URL |
http://www.ann-geophys.net/31/263/2013/http://www.ann-geophys.net/31/263/2013/angeo-31-263-2013.pdf
|
DOI |
10.5194/angeo-31-263-2013
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