Speaker
Dr
Stefan Eriksson
(University of Colorado)
Description
Hall currents generate a characteristic quadrupole out-of-plane
magnetic field at a
single X-line for a weak background guide-field and relatively
symmetric conditions
of plasma density and magnetic field strength across a reconnecting
current sheet.
This is observed as a bipolar perturbation of the out-of-plane magnetic
field (BM)
across the exhaust region as, e.g., reported by Mozer et al. [2002] for
a symmetric
event at the magnetopause on 1 April 2001. Here we present the first
observation of
a tripolar BM perturbation that the Polar satellite encountered within 5
min of the
bipolar event reported by Mozer et al. and in the same subsolar region
of the
magnetopause. The tripolar signature consists of two guide field
depressions
adjacent to an enhanced guide field within the exhaust. Tripolar
signatures have
been reported across solar wind exhausts and explained in terms of
multiple X-lines
at a given current sheet. A dedicated particle-in-cell simulation is
explored to
understand this new magnetopause observation, which occurred for a
mean ratio
BM/BL=0.4 between the background BM and the reconnecting field BL.
Primary author
Dr
Stefan Eriksson
(University of Colorado)
Co-authors
Dr
Alessandro Retino
(Laboratoire de Physique des Plasmas)
Dr
Paul Cassak
(West Virginia University)
