Reconnection as a possible origin of dayside Pc1 magnetic pulsations observed at high latitudes
Abstract
Induction magnetometer observations from Spitsbergen archipelago are combined with data of two other magnetometers located in Scandinavia and the Kola peninsula. We consider seven intervals with very large negative IMF Bz component. For these events, the cusp is expected to be strongly shifted equatorward of its statistical position so that the Barentsburg magnetometer is located well inside the polar cup. For all cases, DMSP particle data indicate that the Barentsburg magnetometer was indeed inside the polar cap, whereas the two other magnetometers were collocated with the ionospheric projections of either the cusp, low latitude boundary layer or boundary plasma sheet. Magnetic pulsations in the Pc1 frequency range were observed around local noon and only in the polar cap. In three cases, for which SuperDARN convection data were available, the Pc1 activity correlated well with intervals of large-scale convection reconfiguration, such that the plasma flow crossing the location of Barentsburg might be associated with newly reconnected magnetic flux tubes drifting tailward. The convection reconfiguration seemed to be caused by a decrease in the IMF By component. We argue that the Pc1 pulsations were associated with the plasma depletion layer within the magnetosheath where, due to the anisotropy of the plasma, the electromagnetic ion cyclotron (EMIC) instability was excited. After reconnection, flux tubes with the unstable plasma turned out to be connected to the Earth's ionosphere and the EMIC waves were seen on the ground as Pc1 bursts.
- Publication:
-
35th COSPAR Scientific Assembly
- Pub Date:
- 2004
- Bibcode:
- 2004cosp...35.3340S