Magnetotail flow bursts: Association to global magnetospheric circulation, relationship to ionospheric activity and direct evidence for localization (original) (raw)

We present multipoint observations of a series of bursty bulk flow events (BBFs) observed by WIND and GEOTAIL positioned in roughly the same local time sector in the magnetotail. Simultaneous IMP8 measurements from the solar wind showed significant amounts of energy coupling into the magnetosphere while the ultraviolet imager (UVI) on POLAR evidenced the energy transfer to the ionosphere. Two major substorms composed of localized electrojet activations, were seen on ground magnetometer networks and UVI. There is a correlation between the magnetotail activity at WIND/GEOTAIL and the ionospheric activity at the local time sector of the two spacecraft. On one occasion tailward bursty flows observed at X=-19 Re by GEOTAIL in the magnetotail were correlated well with an intense brightening of the aurora at the presumed footpoint of GEOTAIL even if there were no significant magnetic signatures at the local ground stations, because of the presumed low ionospheric conductivity at that sector. On another occasion, ground magnetic and auroral activity took place 3 hours of local time away from the WIND/GEOTAIL meridian, explaining the lack of magnetotail energizations at the two spacecraft. On yet another time, no significant flux transport was evidenced at WIND despite the very large transport seen past GEOTAIL. Despite the small intersatellite separation (<∆r WI-GT >=(3.54, 2.88, -0.06) R E ) and the high degree of cross-correlation of the slow (V<100 km/s) flows there is little agreement between individual flow bursts as seen at the two satellites, even in cases when the magnetotail activity is extended. We conclude that the half-scale-size of the transport-bearing flow bursts in the magnetotail is less than 3 R E .