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本文根据Cluster卫星上的粒子成像质谱仪(RAPID)探测器在穿越地球等离子体片过程中的观测数据,统计研究了等离子体片中能量离子能量密度的空间分布(氢离子能量范围从40keV到1500keV,氦离子和氧离子从10keV到1500keV),并且给出了离子能量密度在不同地磁活动时期随GSE-Z向分布的剖面.研究表明能量离子的能量密度以及能量密度的梯度与地磁活动指数Kp之间存在近似线性的关系.观测结果表明形成这种分布变化的主要原因是在地磁活动期间在电流片附近离子能量密度的增加,特别是其中的重离子成分增加更为显著.本文通过一个简化的电流片模型的数值计算,定性地研究了形成能量离子空间分布的机理.计算表明重离子在电流片中可以获得更多的能量,电流片加速可能是形成能量密度分布变化的一种可能的机制.
In this paper, based on the observed data of particle imaging mass spectrometry (RAPID) detector on Cluster satellite in the process of crossing the Earth’s plasma slice, the energy distribution of energy ions in the plasma slice is statistically studied (the energy range of hydrogen ions is from 40keV to 1500keV , Helium ions and oxygen ions from 10 keV to 1500 keV) and gives the profiles of ion energy densities with GSE-Z distribution over different geomagnetic activity periods. The study shows that the energy density of energy ions and the gradient of energy density are related to the geomagnetic activity index Kp The results show that the main reason for this change is the increase of ion energy density in the vicinity of the current sheet during geomagnetic activity, especially the increase of heavy ion components is more significant.Through a simplified , The mechanism of forming the spatial distribution of energy ions is qualitatively studied. The calculation shows that heavy ions can obtain more energy in the current slice. The acceleration of the current slice may be a possibility of forming a variation of the energy density distribution mechanism.