Mechanism Of Electron Acceleration Associated With Dipolarization Fronts In The Eart’s Magnetotail

In order to better understand the electron energization around the dipolarizationfront (DF), we statistically studied lots of DFs from the data provided by the NASA’sTHEMIS spacecraft, which spent8months during the year of2008-2009in theEarth’s magnetotail. The main text has the following five sections.In chapter one, We introduce the backgrounds and current progress ofmagnetosphere, substorms and dipolarizations. We also introduce the THEMISmission, and the minimum variance analysis used to calculate the normal directions.In chapter two, we perform a statistical study on the variation of energeticelectron flux around DFs. We found that: for increasing type DFs, the probabilities ofoccurrence on the dawn side（63%） and on the central region（62%）are both largerthan that on the dusk side（50%）. For the decreasing type DFs there is no suchdependence on the locations.In chapter three, we study the Pitch Angle Distribution of Energetic ElectronsAssociated with DF. We found that:(1) anisotropy factor has a good correlation withthe types of the flux pileup regions（FPRs）: The perpendicular (pancake) distributionis found primarily inside the growing FPR, the field-aligned (cigar) distribution isobserved mainly inside the decaying FPR, inside the steady FPR, which ischaracterized by the constant flow velocity, we observe primarily the isotropicdistribution of energetic electrons.(2) there is no obvious dependence of electronanisotropy on the different sectors of DF.In chapter four, we summarize our work and give the prospect.