Observational Study Of A Complicated Core Field Inside The Magnetotail Magnetic Flux Rope

A large number of explosive energy release processes frequently occurred in the sun-earth space,such as the earth's magnetospheric substorm,solar flare.At present,researchers generally consider these explosive energy release processes mainly pro-duced by magnetic reconnection.Accompanied the process of these explosive energy bursts,some small-scale spiral magnetic structure often can be observed,as were called the magnetic flux ropes.Indicated by the present observations,magnetic flux rope also play an important role in the process of these explosive energy release o For instance,magnetic flux rope can improve the reconnection rate and accelerate particles.Through the analysis of the cluster satellites observation data in the earth magnetotail,the thesis study the magnetic flux rope structures near the magnetic reconnection area in detail,and intensively study that one of magnetic flux ropes with a complicated core field,and provide a reasonable physical explanation on the complex core field.Cluster satellites at the earth magnetotail observed a magnetic reconnection event during 0950-1050UT on August 28,2002.During the crossing of the reconnection region,Cluster satellites clearly detected a quadrupole structure of the Hall magnetic field.Due to the presence of the guide field,this quadrupole structure was distorted.Many magnetic flux ropes were observed by Cluster satellites in this event,and the polarity of the core field of the partial magnetic flux ropes consistent with the polarity of the guide field.One of the magnetic flux ropes had a spatial scale that could match with the satellite spacing,the four satellites respectively passed through the different region of the inner of the magnetic flux rope.Researching on the magnetic data from four satellites,it was discovered that this magnetic flux rope had a complex core field structure.Near the center of the magnetic flux rope,the polarity of the core field consistent with that of the guide field;while near the boundary of the magnetic flux rope,the polarity of the core field consistent with that of the background magnetic field.Such complex core field structure shown that the axis of the magnetic flux rope is bent.Using the electron data from Cluster satellites,we discovered that electron dis-tribution inside the magnetic flux rope appeared anisotropic and that the electron flux paralleled to the magnetic field was larger than that the electron flux was perpendicular to the magnetic field.Through the analysis of the electron distribution data,we consid-ered that the complex electron current existed inside the magnetic flux rope.Using the method of data analysis,we conclude that the magnetic flux rope is distrot produced the observed complex core field structure.