Anomalous dynamics of the extremely compressed magnetosphere during 21 January 2005 magnetic storm

Abstract

The dayside magnetosphere and proton radiation belt were analyzed during unusual magnetic storm on 21 January 2005. We have found that from 1712 to 2400 UT, the subsolar magnetopause was continuously located inside geosynchronous orbit due to strong compression. The compression was extremely strong from 1846 to 2035 UT when the dense plasma of fast erupting filament produced the solar wind dynamic pressure that peaked up to > 100 nPa, and during the first time, the upstream solar wind was observed at geosynchronous orbit for almost 2 h. Under the extreme compression, the outer magnetosphere at L > 5 was pushed inward, and the outer radiation belt particles moved earthward, became adiabatically accelerated, and accumulated in the inner magnetosphere at L < 4 that produced the intensified ring current with an exceptionally long lifetime. The observations were compared with predictions of various empirical and first-principles models. All the models failed to predict the magnetospheric dynamics under the extreme compression when the minimal magnetopause distance was estimated to be~3 RE. The inconsistencies might result from distortions of plasma measurements by extreme heliospheric conditions consisting in very fast solar wind streams and intense fluxes of solar energetic particles. We speculated that anomalous dynamics of the magnetosphere could be well described by the models if the He abundance in the solar wind was assumed to be > 20%, which is well appropriate for erupting filaments and which is in agreement with the upper 27% threshold for the He/H ratio obtained from Cluster measurements.

Saturation of the magnetosphere during superstorms: new results from the magnetogram inversion technique

“…The obtained (P d ) saturation in all the events with both signs of B z and an increase in its level during the IMF turn from north to south (Figure 6, f -8, f) corresponds to the observed [Kovner, Feldstein, 1973;Shue et al, 1998;Dmitriev et al, 2014] additional compression of the magnetopause in such a turn and our assumption [Mishin et al, 2016] about its associated polar cap area growth The presence of the (P d ) saturation under northward IMF, when the effect of the dayside reconnection is minimal, is most pronounced during the 2000 storm with high P d pulses observed after the IMF northward turn, and also immediately after SC during the passage of the SW compression region during the 2003 and 1998 storms. The intersection of the  saturation levels at different signs of B z (panels c and e in Figure 6) corresponds to the time span of the IMF northward turn upon the passage of the compression region after SC, when E m and P d variations cannot be considered as independent (see Section 2.1).…”

“…Then the enhancement almost stops, after reaching critical values of 1) interplanetary fields (electric E SW and/or southward IMF component B S ) [Siscoe et al,. 2002;Borovsky et al, 2009;Kan et al, 2010;Lyatsky et al, 2010;Wilder et al, 2011;Gao et al, 2013 and references therein), and 2) dynamic pressure P d , as shown in [Karavaev et al, 2012a, b;Mishin et al, 2015Mishin et al, , 2016. This phenomenon of slowdown in the enhancement of U PC and  is termed the saturation of the polar cap potential [Siscoe et al, 2002] and its area [Merkin, Goodrich, 2007].…”

“…Moreover, by the total saturation of  we mean the absence of its growth when SW rises. Mishin et al [2015Mishin et al [ , 2016 have noted a possible relationship of this phenomenon with the finite compressibility of the magnetosphere, namely with the fact that its dayside boundary is rarely observed inside the geostationary orbit [Shue et al, 1997[Shue et al, , 1998Kuznetsov, Suvorova, 1998;Dmitriev et al, 2014]. Most authors consider the saturation phenomenon as the slowdown of momentum and energy transfer through the dayside magnetopause depending on interplanetary fields E SW or B z .…”

Saturation of the magnetosphere during superstorms: new results from magnetogram inversion technique

“…6, e -8, e) соответствует наблюдаемому [Kovner, Feldstein, 1973;Dmitriev et al, 2014] дополнительному сжатию магнитопаузы при таком повороте и нашему предположению о связанном с ним увеличении площади полярной шапки. Наличие насыщения (P d ) при 36 34 северном ММП, когда влияние дневного пересо-единения минимально, наиболее отчетливо видно во время бури 2000 г., когда большие импульсы давления P d наблюдались после поворота ММП на север, а также сразу после SC во время прохождения области сжатого СВ во время двух других бурь 2003 и 1998 г. Пересечение уровней насыщения  при разных знаках B z (панели в и д на рис.…”

“…При этом под полным насыщением  мы будем понимать отсутствие его роста при усилении СВ. В работе [Mishin et al, 2015 отмечена возможная связь этого явления с конечной сжимаемостью магнито-сферы, а именно с тем, что ее дневная граница редко наблюдается внутри геостационарной орбиты [Shue et al, 1997Dmitriev et al, 2014]. Большая часть авторов рас-сматривает явление насыщения как замедление про-цессов переноса импульса и энергии через дневную магнитопаузу в зависимости от межпланетных по-лей E СВ или B z .…”