Publication Date:
2016-06-25
Description:
We report on novel features of the saturation process of the polar cap magnetic flux and Poynting flux into the magnetosphere from the solar wind during three superstorms. In addition to the well-known effect of the interplanetary electric ( E sw ) and southward magnetic ( IMF B z ) fields, we found that the saturation depends also on the solar wind ram pressure P d . By means of the magnetogram inversion technique and a global MHD numerical model PPMLR, we explore the dependence of the magnetopause standoff distance on ram pressure and the southward IMF. Unlike earlier studies, in the considered superstorms both P d and B z achieve extreme values. As a result, we show that the compression rate of the dayside magnetosphere decreases with increasing P d and the southward B z , approaching very small values for extreme P d ≥ 15nPa and B z ≤ −40nT. This dependence suggests that finite compressibility of the magnetosphere controls saturation of superstorms.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics