Magnetic reconnection is one of the key processes taking place in a thin current sheet in the magnetotail. In contrast to magnetopause reconnection, where the shear component can be significant, magnetitail reconnection has been considered to be described in a 2-D geometry. however, such 2-D reconnection should not always be the case, as is suggested by a Cluster observation, when a strong guide field was observed during a fast flow interval. During the event, an intense current layer took place. A peak current density of 182 nA/m2 was detected (panel (c) in the figure), which was hte largest current density obtained from the four-point Cluster analysis in the magnetotail. In this thin ölayer, which had a scale size comparable to the ion-inertia length, the current was flowing mainly antiparallel to the field (panel (c)). The event was associated with parallel heating of electrons with assymetries (panels (a) and (b)), which suggests that electrons moving along the field lines can contribute to a strong dawn-to-dusk current.

(from Nakamura et al., J. Geophys. Res., 113, A07S16, doi:10.1029/2007JA012760, 2008.)

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