Experimental Evaluation of Multi-spacecraft Data Analysis Techniques in a Laboratory Plasma
Authors: Jongsoo Yoo and Masaaki Yamada
Abstract:
The Magnetic Reconnection Experiment (MRX)[1] has been utilized to assess the effectiveness of
minimum variance analysis on the magnetic field (MVAB) and boundary-crossing time analysis (BCTA).
The neutral sheet is swept, or jogged, in a controlled manner with respect to the stationary probes
by pulsed internal coil currents. Magnetic field data from measurement points resembling data from
multi-spacecraft flying though a reconnecting current sheet is used to check both techniques to deduce
a proper normal vector. We examine discharges with the two-dimensional (2-D) X-line structure as well
as cases in which a flux rope forms within the layer. All discharges are in a two-fluid regime in which
electrons are magnetized but not ions. Boundary-crossing time analysis with four sample measurement
points forming a tetrahedron generates a reasonable unit normal vector and relative velocity along the
normal vector for all of the tested cases. On the other hand, MVAB sometimes fails to predict a proper
normal direction. This is because the X-line magnetic geometry is fundamentally 2-D or 3-D. However,
the direction along the reconnecting field determined by MVAB does not deviate much from the real
magnetic geometry documented by 2-D magnetic probe arrays and one additional probe at a different
toroidal location. Based on these observations, we suggest a procedure for determining a local coordinate
system for data from the Magnetospheric Multi-Scale (MMS) mission when spacecraft passes through a
reconnecting current sheet. The distance between measurement points on the order of the ion skin depth
(c/ωpi) is pertinent to determination of the magnetic geometry.
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Submitted to: Journal of Geophysical Research Space Physics (March 2012)
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