Profile of strong magnetic field By component in magnetotail current sheets

The strong magnetic field B-y component (in GSM coordinates) has been increasingly noticed to play an important role in the dynamics of tail current sheet (CS). The distribution profile of strong B-y components in the tail CS (i.e., those with guide field), however, is not well known. In the present work, by using the simultaneous multipoint observations of Cluster satellites, the profile of a strong B-y component in tail current sheets is explored, through detailed case studies, as well as in a statistical study. It is discovered that around the midnight meridian, the strength of the strong B-y component, i.e., |B-y|, is basically enhanced at the center of the CS relative to that in the CS boundaries and lobes and forms a north-south symmetric distribution about the center of CS. Generally, however, for strong guide field cases in the non-midnight meridian, the profile of B-y strength basically becomes north-south asymmetric, the strength of the B-y component in the northern side of the CS is found to be either stronger or weaker than that in the counterpart southern side. By considering the modulation of the tail flaring magnetic field with magnetic local time, we propose an interpretation to account for the variation of the B-y-profile, which is supported by the statistical survey. These results offer an observation basis for further studies.