资源环境科技发展态势分析平台

Observations from Magnetospheric MultiScale (similar to 8 Re) and Van Allen Probes (similar to 5 and 4 Re) show that the initial dayside response to a small interplanetary shock is a double-peaked dawnward electric field, which is distinctly different from the usual bipolar (dawnward and then duskward) signature reported for large shocks. The associated ExB flow is radially inward. The shock compressed the magnetopause to inside 8 Re, as observed by Magnetospheric MultiScale (MMS), with a speed that is comparable to the ExB flow. The magnetopause speed and the ExB speeds were significantly less than the propagation speed of the pulse from MMS to the Van Allen Probes and GOES-13, which is consistent with the MHD fast mode. There were increased fluxes of energetic electrons up to several MeV. Signatures of drift echoes and response to ULF waves also were seen. These observations demonstrate that even very weak shocks can have significant impact on the radiation belts.

Plain Language Summary Very fast moving clouds of charged particles are ejected from the Sun when it is active. Shock waves often develop at the cloud front as it plows through the solar wind. When the shock hits the Earth's magnetic field, it can push the Earth's magnetic shield inside the distance where many communication and weather satellites orbit. The energy associated with the shock can also very rapidly increase the energy of electrons trapped in the Earth's magnetic field in the Van Allen Radiation belts. These electrons can damage satellites. We have used four satellites arrayed at different locations on the dayside of the Earth's magnetic field to show, for the first time, that small shocks have a different effect than the large shocks that are usually studied but that even small shocks can produce relativistic electrons.