Multi-spacecraft observations of earthward flow bursts  

作　　者：MA YuDuan CAO JinBin REME Henry DANDOURAS Iannis DUNLOP Malcolm LUCEK Elisabeth 

机构地区：[1]School of Astronautics,Beihang University,Beijing 100191,China [2]SOA Key Laboratory for Polar Science,Polar Research Institute of China,Shanghai 200136,China [3]Centre d'Etude Spatiale des Rayonnements,Toulouse 31028,France [4]RutherforAppleton Laboratory,Oxfordshire,UK [5]Blackett Laboratory,Imperial College London,London SW72AZ,UK

出　　处：《Science China(Technological Sciences)》2012年第5期1305-1311,共7页中国科学（技术科学英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 40931054, 41174141 and 40904042);the National Basic Research Program of China ("973" Project)(Grant No. 2011CB811404);Specialized Research Fund for State Key Laboratories (Grant No. KP201104);supported by Chinese Academy of Sciences (CAS) visiting Professorship for Senior International Scientists (Grant No. 2009S1-54)

摘　　要：On the basis of the plasma, electric and magnetic fields jointly observed by Cluster and the Double Star TC-I spacecraft in the Earth＇s magnetotail, we have investigated the earthward flow bursts by introducing the momentum equation in the X-direction in the ideal conditions of magneto hydrodynamics （MHD）. One earthward flow burst with a peak in excess of 500 km/s was selected, when the four spacecraft of Cluster were located around -16 RE and TC-1 was located around -10 RE in the X-direction. The inter-spacecraft distances in Y and Z directions were smaller than the statistical spatial scales of the bursty bulk flows. When the Y components of E and -VxB were compared, there was no clear breakdown of the frozen-in condition during the earthward flow burst. With the measured plasma and magnetic parameters from two spacecraft at different positions in the magnetotail, the X component of the pressure gradient was calculated. Magnetic tension was calculated using the mag- netic field measured at four points, which could be compared with the assumed constant in the past research with single satel- lite. When the pressure gradient and the magnetic tension were put into the MHD momentum equation, some samples of the earthward flow bursts were accelerated and some were decelerated. The braking process of the earthward flow burst was more complicated than what the past results had shown. The accelerated samples accounted for about one third of the whole earth- ward flow bursts and discontinuously located among the decelerated elements. The original single earthward flow burst event might be split into several short flow bursts when it was moving to the Earth. Our results may partly illustrate that the duration of fast flows during three phases of substorm becomes short near the Earth. The results are consistent with the past results that fast flows intrude to places earthward the typical braking region.

关 键 词：flow burst pressure gradient magnetic tension BRAKING 

分 类 号：TM752[电气工程—电力系统及自动化] V476.2[航空宇航科学与技术—飞行器设计]