The Magnetic Local Time Distribution of Storm Geomagnetic Field Disturbance Under Different Conditions of Solar Wind and Interplanetary Magnetic Field

摘要

The magnetic local time (MLT) distributions of the horizontal geomagnetic disturbance (ΔH) are investigated with the SuperMAG data set during 330 magnetic storms from 2000 to 2015. Then the MLT distributions of ΔH are verified and interpreted with the SuperMAG-based partial ring current indices (SMR indices) and the Burton equation. It is shown that the ΔH is positive at most MLTs and slightly stronger on the dayside during the initial phase. Such distribution might be mainly attributed to the global positive impact of the magnetopause currents, while the ring current (RC) only produces weak negative disturbances, which are slightly stronger on the duskside. In the main phase, the ΔH decreases prominently with the peak on the duskside. The RC particles injection plays a major role, especially for large solar wind electric field (E_(SW)). The region with ΔH larger than -20 nT is concentrated on the dawnside for small E_(SW), which might be attributed to earthward bursty bulk flows. Besides, larger solar wind dynamic pressure might cause stronger disturbances under the same magnitude of E_(SW). In the recovery phase, the ΔH is weaker and more uniform distributed than in the main phase for negative E_(SW). For positive E_(SW), similar dawn-dusk asymmetry occurs as that in the main phase, but the peak of strongest disturbance tends to weaken and move toward the dayside. Based on the dawn-dusk asymmetric decay rate derived from the Burton equation, it is speculated that the contribution of partial RC might be no less than the FACs.