The evidence for the evolution of interplanetary small flux ropes: Boundary layers

We have examined the Wind data in 1996 and identified 21 small interplanetary magnetic flux ropes (SIMFRs), and all the 21 SIMFRs have boundary layer structures. The durations of the boundary layers varied from several minutes to 30 minutes. These boundary layers also have properties of high proton temperature, density, and plasma beta. These boundary layers are formed by magnetic reconnections. In addition, in three events magnetic reconnections were occurring inside the boundary layers. It indicates that the flux rope structures have propagated for some period of time, and their boundaries were still evolving through interaction with the background solar wind. Namely it is very possible that the SIMFRs came from the solar corona.