Current sheet crossings in the distant magnetotail

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Abstract
A computer search of crossings of the field reversal region in the middle of the distant magnetotail has been done with ISEE‐3 data. We have found that the instantaneous direction of the magnetic field at the crossings Bz is northward on average at a distance of 220 RE, with moderate values of the plasma flow. This result suggests that the magnetic field lines are closed; since the flow is tailward, the Dungey model with a steady state reconnection line across the magnetotail earthward of the spacecraft is invalidated. Our result gives strong support to a model in which tailward boundary layer flow provides the viscous interaction proposed by Axford and Hines. At higher values of the plasma velocity we do find negative values of Bz, a result consistent with the existence and tailward motion of plasmoids; these can be created by a form of localized magnetic merging which is three dimensional and time‐dependent. The latter differs essentially from steady state reconnection in that here curl E plays a crucial role, as is obvious from a careful consideration of Poynting's theorem. This does not invalidate the denial of steady state reconnection.

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