Characteristics Of Electron Distribution Functions In Magnetic Cloud Boundary Layers

Based on the magnetic cloud events detected by WIND spacecraft from 1995 to 2006, we study the patterns of electron flows,characteristics of the electron distribution functions as well as their relationships to the heating and acceleration of electrons in the magnetic clouds boundary layers (MCBLs). The main results are as follows. Firstly, there are several types of electron flow patterns in the MCBLs. Secondly, compared with the background solar wind and the magnetic cloud body, the thermal core parts of the electron velocity distribution functions usually increase, together with increasing of superathermal electrons in directions perpendicular to the magnetic field and either parallel or anti-parallel to the magnetic field. Furthermore, the flux of energetic electrons increase in almost ten percent of the MCBLs. Thirdly, by comparisons of the modifications to the electron distribution functions by MCBLs and interplanteray shocks ahead of magnetic clouds, it suggests that the two structures result from different mechanisms. Lastly, we make investigation on the relationships between the enhancements of wave activities and electron distribution functions as well as ion fluxes. These observations and comparisons indicate further that magnetic clouds are important dynamical structures possibly associated with magnetic reconnection as previous studies on MCBLs.