Magnetic flux ropes at planetary magnetopauses

Abstract:

Magnetic flux ropes at the magnetopause are generated as a result of magnetopause reconnection involving more than one X-line, and constitute a subgroup of flux transfer events which are believed to result from transient, localized, and/or multiple X-line reconnection, i.e., time-dependent forms of magnetopause reconnection. Single X-line reconnection at the low-latitude magnetopause erodes the dayside closed field lines and contributes to magnetic flux transport into the magnetotail, which forms the basis for dynamic phenomena in the magnetosphere such as substorms and storms. On the other hand, multiple X-line reconnection can produce the field lines of various topologies and/or can cause complex interactions of reconnection jets or reconnected flux tubes, thus possibly reducing the efficiency of magnetic energy transfer into the tail. This presentation discusses in situ observations at the terrestrial, Hermean, and Kronian magnetopauses and models for the generation, of magnetic flux ropes. In particular, we emphasize that magnetic field (e.g., bipolar) signatures alone cannot be taken as evidence for the flux ropes, and plasma signatures (Alfvenic ion jets, electron pitch-angle anisotropy, etc.) help identify their topological structure. We also present our recent studies using multi-spacecraft (Cluster or THEMIS) measurements at the terrestrial magnetopause for the reconstruction of their two-dimensional and three-dimensional structures based on the Grad-Shafranov and magneto-hydrostatic equations, respectively.