Oleg Troshichev
Arctic and Antarctic Research Institute
Russia
Title: Space weather monitoring and now casting by ground-based means
Biography
Biography: Oleg Troshichev
Abstract
The polar cap (PC) magnetic activity index was approved by International Association of Geomagnetism and Aeronomy (IAGA) in 2013 as a new international index assigned to monitor the energy that enters into the magnetosphere during 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 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 РС index growth, (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 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 is practically absent, in spite of actual substorm onset related to the PC index rise; in these cases the actual solar wind, measured in the Lagrange point, passes by the magnetosphere. It implies that 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.