Abstract
Abstract. At approximately 08:25 UT on 5 April 2010, a CME-driven shock compressed Earth's magnetosphere and applied about 15 nT of southward IMF for nearly an hour. A substorm growth phase and localized dipolarization at 08:47 UT were followed by large dipolarizations at 09:03 UT and 09:08 UT, observed by GOES West (11) in the midnight sector, and by three THEMIS spacecraft near X=−11, Y=−2 RE. A large electric field at the THEMIS spacecraft indicates so much flux transfer to the inner magnetosphere that "overdipolarization" took place at GOES 11. This transfer is consistent with the ground and space magnetic signature of the substorm current wedge. Significant particle injections were also observed. The ensemble of extreme geophysical conditions, never previously observed, is consistent with the Near-Earth Neutral Line interpretation of substorms, and subjected the Galaxy 15 geosynchronous satellite to space weather conditions which appear to have induced a major operational anomaly.
Highlights
IntroductionGeotail being near the Earth-Sun line at a distance of 14.7 RE, only approximately 100 s were required to translate its solar wind observations to the magnetopause (Fig. 1c)
The shock associated with the coronal mass ejection of 3 April 2010 arrived at Earth at approximately 08:25 UT on 5 April 2010
Despite little change in solar wind dynamic pressure, and continued large negative IMF BZ, which persisted until northward turning at roughly 09:30 UT, tail stretching did not resume in the period following the overdipolarization
Summary
Geotail being near the Earth-Sun line at a distance of 14.7 RE, only approximately 100 s were required to translate its solar wind observations to the magnetopause (Fig. 1c). The magnetic field behind the shock was initially slightly northward, but BZ quickly turned to about −13 nT. Increase of plasma density from about 4 to over 10 ions/cc, and of speed from about 550 to 700 km s−1, led to a dynamic pressure increase from about 2 nPa to 10 nPa, and compression of the magnetosphere. Due to short duration of southward IMF, the resulting storm was of low intensity (Mostl et al, 2010). The strong southward field and high dynamic pressure in the sheath immediately following the ICME shock led to impressive short-term effects as described here
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