冷而密的等离子体片及其对磁尾等离子体片分布特性的影响

地球磁尾等离子体片在太阳风-磁层耦合过程中起着重要的作用，其中冷而密的等离子体片是地磁活动平静期太阳风等离子体进入磁层的重要区域.以往的研究通常没有利用局地探测数据针对冷而密的等离子体片发生率在地心太阳磁层坐标系（GSM）中xy平面分布的统计分析.本文利用GEOTAIL卫星1996-2016年的局地测量数据，给出了等离子体片密度、温度及冷而密的等离子体片发生率的二维分布.与温度具有晨昏对称分布不同，等离子体片数密度呈现明显的晨昏不对称性，并且冷而密的等离子体片发生率在晨侧较高. 

Cold-dense Plasma Sheet and Its Impact on the Spatial Distributions of the Magnetotail Plasma Sheet ormalsize

Plasma sheet plays an important role in the coupling of solar wind and Earth magnetosphere, and the Cold-Dense Plasma Sheet (CDPS) is an important evidence of solar wind entry during the geomagnetic quiet time. However, there are handful statistical analyses using in situ observations to investigate the 2D profile of ion number density, temperature of plasma sheet and the CDPS occurrence rate in the xy plane of GSM coordinate. The Geotail data from 1996 to 2016 are used to fill that blank. The 2D profile of ion density, temperature of plasma sheet and the CDPS occurrence rate are plotted. A dawn-dusk asymmetry is seen in the 2D profile of ion density and in the cold-dense plasma sheet occurrence, but not seen in the 2D profile of ion temperature. The dawn-dusk asymmetry of ion density is more clear during the geomagnetic quiet time than that during the geomagnetic active time. Furthermore, the possible affect caused by the CDPS on the 2D profile of ion number density and temperature of the plasma sheet are investigated.