Cluster as current sheet surveyor in the magnetotail

A novel analysis technique is presented to estimate the current sheet thickness unambiguously and directly, with- out associating time series data with spatial structure. The technique is a combination of eigenvalue analysis and mini- mum variance estimator adapted to Harris current sheet ge- ometry, and needs one-time, four-point magnetic field data as provided by the Cluster spacecraft. Two current sheet param- eters, thickness and distance to the spacecraft, can be deter- mined at each time step of the magnetic field measurements. An example is shown from a Cluster magnetotail crossing under quiet magnetospheric conditions, yielding the result that the current sheet thickness is on the scale of the pro- ton gyroradius. The analysis technique can also be used to track the dynamical evolution of the current sheet structure in three dimensions.

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