Evidence for closed structures at the magnetopause: the case for multiple reconnections.

We analyze two LLBL crossings made by Interball Tail satellite under southward magnetosheath magnetic field. Observed ion velocity distributions within LLBL include: (a) D-shaped distributions, (b) ion velocity distributions consisting of two counter-streaming components of magnetosheath-type, and (c) distributions with three components one of which has nearly zero parallel velocity and two counter-streaming components. We interpret these distributions as a natural consequence of the formation of spiral magnetic flux tubes consisting of a mixture of alternating segments originating from the magnetosheath and from magnetospheric plasma. The shapes of ion and electron velocity distributions and their evolution with decreasing number density in LLBL indicate that a significant part of LLBL is located on magnetic field lines of long spiral flux tube islands at the magnetopause, as has been proposed and found to occur in magnetopause simulations. Anomalous magnetosheath-like plasma flow with Bz component opposite to magnetosheath one was observed while IMF Bz remained negative. We consider these observations as evidence for multiple reconnections between magnetosheath and magnetospheric flux tubes.