Plasma and magnetic field characteristics of magnetic flux transfer events

Abstract

Plasma and magnetic field data from ISEE 1 and 2 are examined for 5 passes of the magnetopause region at 20°–40° northern latitudes and ∼0800 to 1215 hours local time. These intervals contained a total of 15 well‐defined magnetic flux transfer events, which occurred in the magnetosheath as well as the magnetosphere. In either case, flux transfer events are characterized by a mixture of magnetosheath and magnetospheric particles. This fact strongly supports the hypothesis that flux transfer events represent encounters of reconnected flux tubes. Inside all of the studied events, the magnetic field strength as well as the sum of plasma and magnetic pressures is strongly enhanced. This excess pressure appears to be balanced by the tension of the ambient magnetic field lines as they are draped around the reconnected flux tube. The different observed magnetic field signatures are consistent with expectations for encounters of the flux tubes at different relative locations. Only those events that appear to be crossings of the flux tube close to its magnetopause crossing show large (∼100 km s−1) plasma flow speed enhancements. These increased velocities are restricted to the trailing portion of the events and are directed at large angles with respect to the magnetic field. One hypothesis is that the increased flow speeds are caused by continued reconnection at the low‐latitude boundaries of the flux tubes.