On the relationship between bursty flows, current disruption and substorms

A current disruption (CD) event was observed by the Geotail spacecraft at (X, Y)(GSM)=(-10.0, 1.9) R-E within 1 min from the onset of a substorm. The event was selected as one of four near-Earth current disruption events identified in a search of three years of Geotail data. Fast ion flows accompanied the magnetic field dipolarization, rendering this event a near-Earth bursty bulk flow (BBF) event. The gradient anisotropy of the 30-44 keV ions at the onset of the flow is consistent with an Earthward motion of the heated plasma and agrees with the direction of Aux and energy transport. The aurora and the associated electrojet moved from low to high latitudes during substorm expansion. Our observations show that CDs and BBFs are qualitatively similar phenomena in the near-Earth tail, both associated with poleward-moving (classical) auroral substorms.