Line A Preliminary Study Of The Interaction Of Interplanetary Magnetic Cloud And The Heliospheric Current Sheet

There is a close relationship between magnetic clouds and the heliospheric current sheet.When propagating from Sun to Earth,magnetic clouds, especially the ones who originated near the solar equator, may interact with large-scale heliospheric current sheet.We call this phenominon"collision interaction". Studies of interactions between magnetic clouds and background media will help understand the mechanism of formation and evolution of magnetic clouds, as well as their effect on the Earth's magnetosphere, and help to understand the causal relationship between geomagnetic disturbances and solar activities,which can be helpful to the research of Sun-Earth physics. This paper is based on 105 magnetic cloud events detected by WIND spacecraft from 1995 to 2007.According to whether the magnetic cloud"collides"with the heliospheric current sheet,we devide the magnetic cloud events into two types,which are"collided"and"not collided". The preliminary results are as follows.Firstly,There are 51 magnetic clouds which may have collided with heliospheric current sheet, which is about 49% of the total incident.Secondly,when a magnetic cloud"collides"with the heliospheric current sheet,the region between magnetic cloud and heliospheric current sheet tend to emerge evidences of inhancement of dynamic interaction ,such as appearance of local magnetic field direction discontinuity structures, decreased magnetic field strength,increased proton temperature,irrupt change of some components of proton velocity,enhancement of ion-acoustic waves or Langmuir waves.These phenomina are possibly related to magnetic reconnection in the"colliding"interaction regions.In case of not collided,these characteristics are not evident. Thirdly, in at least 15 cases,the magnetic polarity of the background magnetic fields in front of the magnetic cloud and the one behind the magnetic cloud are opposite,or the reverse point of magnetic polarity was inside the magnetic cloud,that means the magnetic cloud was moving cross the HCS.Lastly,bright fronts and bright cores of CMEs have been seen in some events.These preliminary results are helpful to understanding the process of interaction between magnetic cloud and heliospheric current sheet, however further analysis and numerical simulations are still required.