Global magnetospheric response to an interplanetary shock: THEMIS observations

摘要

We investigate the global response of the geospace plasma environment to aninterplanetary (IP) shock at ~02:24 UT on 28 May 2008 from multipleTHEMIS spacecraft observations in the magnetosheath (THEMIS B and C), themid-afternoon magnetosphere (THEMIS A), and the dusk magnetosphere (THEMIS Dand E). The interaction of the transmitted IP shock with the magnetospherehas global effects. Consequently, it can affect geospace plasmasignificantly. After interacting with the bow shock, the IP shock transmitteda fast shock and a discontinuity which propagated through the magnetosheathtoward the Earth at speeds of 301 km s?1 and 137 km s?1, respectively. THEMIS Aobservations indicate that the IP shock changed the properties of aplasmaspheric plume significantly. The plasmaspheric plume density increasedrapidly from 10 to 100 cm?3 in 4 min and the ion distributionchanged from an isotropic to a strongly anisotropic distribution.Electromagnetic ion cyclotron (EMIC) waves observed by THEMIS A are mostlikely excited by the anisotropic ion distributions caused by the IP shockimpact. THEMIS A, but not D or E, observed a plasmaspheric plume in thedayside magnetosphere. Multiple spacecraft observations indicate that thedawn-side edge of the plasmaspheric plume was located between THEMIS A and D(or E).