The Interplanetary Origins Of Geomagnetic Storm With Dst≤-50Nt In2007-2012

Geomagnetic storm is a major class of disastrous space weather events. Severe ge-omagnetic storm could destroy communication and electric power systems. Generally, interaction of southward interplanetary magnetic field in solar wind and magnetosphere of Earth is the main cause of geomagentic storms, while a variety of interplanetary struc-tures may contain southward magnetic field. Thus, researching interplanetary origins of geomagnetic storms is a key factor in understanding and forecasting geomagnetic storms. In this paper, all moderate and over geomagnetic storm events between2007and2012with Dst≤-50nT are indentified and studied. In these six years, there are totally51geomagnetic storms, of which9storms are strong geomagnetic storms with Dst≤－1OOnT. Comparing with the same period in last solar cycle when the solar activity was stronger, number of geomagnetic storms was significantly reduced. A detailed list of these51geomagnetic storms was established. Detailed analysis of these storms shows that65% geomagnetic storms with Dst≤-50nT were caused by interplanetary coronal mass ejections (ICMEs) and their corresponding structures such as shock, sheath and so on, while31% were caused by corotating interaction re-gions (CIRs). This result is consistent with previous. In particular, during this so-lar cycle that has lower activity level, CIRs casued nostrong geomagnetic storms with Dst≤－100nT while ICMEs and their coirresponding structures casued no super geo-magnetics storms with Dst≤-200nT, which indicates that lower solar activity leads to weaker geomagnetic effect caused by CMEs and CIRs. Furthermore, analysis of ge-omagnetic storms numbers distribution with solar cycle period shows that CIRs became the main cause of storms in solar cycle minimum while ICMEs remained the main cause in solar cycle maximum and rising period. To understand how these solar wind distur-bances progress in the interplanetary space, various models have been developed to ob-tain the parameters of interplanetary magnetic field (IMF), solar wind plasma, CMEs, CIRs, Shocks and other disturbances. In this article, we give a brief review of these models, they are:backgroud IMF obtaining models, background solar wind obtaining models, CME kinematic parameters obtaining models, CME deflection models, CME (shock) propagation models and numerical MagnetoHydroDynamic (MHD) simulation methods. These models connect observation at1AU with that of the sun, and then form the necessary supports for tracking solar wind disturbances to the sun.