Coordinated observation of the dayside magnetospheric entryand exit of the THEMIS satellites with ground-basedauroral imaging in Antarctica

摘要

[1] Data from the five-satellite Time History of Events and Macroscale Interactionsduring Substorms (THEMIS) constellation suitably located to study solar windmagnetospheric coupling during the austral winter of 2007 were compared to datafrom ground-based all-sky imagers (ASIs) at South Pole (74° magnetic latitude) andat AGO-1 (80° magnetic latitude). The THEMIS constellation entered and exited themagnetosphere near magnetic midday on 10 and 12 August 2007, respectively. On 12 August interplanetary magnetic field (IMF) (Br > 0) the dayside aurora was locatedmore poleward between AGO-1 and South Pole. The THEMIS satellites traversing themagnetopause saw it move in and out several times during the satellite crossings. Theinward motion of the magnetopause was sometimes correlated with equatorward expansions of the aurora and sometimes with solar wind pressure pulses as seen byGeotail. The B_z> 0 auroral latitude was consistent with dayside cusp "spot" seen bythe IMAGE spacecraft and had been associated with footprints of "steady state" lobereconnection. The aurora consisted of a continuous stream of poleward moving auroralforms (PMAF) even during a period of slightly B_z > 0 and B_y= 0. On 10 August 2007IMF B_z < 0 the dayside aurora was located more equatorward, over South Pole, and theTHEMIS satellites crossed the bow shock from the magnetosheath into the solar wind.Negative B_z pulses observed at the satellite were correlated with large polewardexpansions of the dayside aurora consistent with reconnection in the subsolar regionaccompanied by simultaneous plasma density increases at THEMIS B satellite consistentwith outward radial motion of the bow shock.