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<專題討論>2018/3/8(四)14:10綜合大樓2樓48218教室演講 : Prof. O. A. Troshichev(Arctic and Antarctic Research Institute, St/Petersburg, Russia)

張貼者:2018年3月4日 下午6:57Dabby Lu   [ 已更新 2018年3月4日 下午7:07 ]
講題:The polar cap magnetic activity (PC) index as an indicator of the solar wind energy incoming into the magnetosphere.
摘要:The polar cap (PC) magnetic activity index was approved by the International Association of Geomagnetism and Aeronomy (IAGA) in 2013 as a new international index assigned to monitor the energy that enters into the magnetosphere under the solar wind-magnetosphere coupling. The following experimental data form the basis for this statement: (1) the PC index strongly follows the time evolution of interplanetary electric field (EKL) reduced to the magnetopause, (2) delay time ΔT in response of PC index to EKL variations is controlled by the EKL field growth rate (dEKL/dt), (3) magnetic storms and substorms are always preceded and accompanied by a growth in РС index, (4) substorms and magnetic storms start to develop as soon as the PC index exceeds the threshold level of 1.5 mV/m, (5) the substorm sudden onsets are commonly associated with a sharp increase in the PC (and EKL) growth rate, (6) the solar wind drivers (ICMEs or SIRs) determine the type of magnetic storm, such as “classic” storm, related to ICME impact, with well-defined PC maximum and clearly expressed one maximum of depression, “pulsed” storm, related to SIR impact, with periodically repeating oscillations in PC and geomagnetic field depression, and “combined storms”, which are regarded as effect of simultaneous ICME and SIR action, (7) maximal depression of magnetic field responds to maximal PC value with a delay of ~1 hour, the storm intensity (Dstmin) being linearly depending on PCmax value. In ~10% of the substorm events the correlation between EKL and PC was practically absent, in spite of the PC index rise before the substorm onset, which means that solar wind, measured in the Lagrange point, passes by the magnetosphere in these cases. Therefore the РС index can be used also to verify whether or not the solar wind measured in Lagrange point L1 is in contact with the magnetosphere.

All these statistically justified relationships testify that the PC index is an indicator of the solar wind energy incoming into the magnetosphere. In this context, the PC index can be successfully used as a new reliable ground-based technique for exploration of short-term changes in space weather and magnetosphere state.

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Dabby Lu,
2018年3月4日 下午7:07
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