"Evidence
for closed structures at the magnetopause: a case for multiple
reconnections
O.
L.Vaisberg1, L. A.
Avanov1,2, T. E. Moore3,
and V. N. Smirnov1
1
Space Research Institute, Moscow, Russia
2 NSSTC / MSFC, Huntsville, AL, USA
3
Goddard Space Flight Center, Greenbelt, MD, USA
Abstract:
Classic concept of magnetic merging is represented by pair of flux tubes originating from two interacting magnetic fields reconnected at X-line. This type of reconnection between interplanetary magnetic field and magnetospheric magnetic field received very substantial confirmation from observations. Another concept of reconnection so called multiple reconnection was proposed and shown possible by numerical simulation but did not receive observational support. We use Interball-Tail observations of ion velocity distributions within magnetospheric boundary layer as tracers of magnetic topology.
Observed ion velocity distributions within LLBL include: (a) D-shaped distributions, (b) ion velocity distributions consisting of two counterstreaming magnetosheath-type, and (c) distributions with three components one of which has nearly zero Vpar and two counter-streaming components. We consider these observations as evidence for multiple reconnections between magnetosheath and magnetospheric flux tubes. The shapes of ion velocity distributions and their evolution with decreasing number density in LLBL indicate that significant part of LLBL is located on magnetic field lines of long spiral flux tube islands at the magnetopause. 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. Observation of anomalous magnetic flux tube in the flow of plasma around magnetosphere confirms this interpretation. Our observations and analysis support concept of multiple reconnection at the magnetopause.