日冕物质抛射的偏转特性研究

A Study on Deflection Characteristics of Coronal Mass Ejection

日冕物质抛射(CME)是巨大的、携带磁力线的泡沫状气体,在几个小时中被从太阳抛射出来的过程。日冕物质抛射伴随着大量带电粒子和辐射的释放,这些物质进入日地空间,对日地空间的磁场造成很大扰动;当它们传播到地球附近时,则严重影响地球的磁场,产生磁暴,也对空间和地面的电子设备造成干扰。日冕物质抛射在传播过程中如果发生偏转,将影响它对地有效性。因此研究日冕物质抛射的偏转特性,对预报日冕物质抛射对日地空间的影响具有重要意义。主要利用2007年10月8日STEREO卫星的日冕物质抛射观测资料,结合全日面线性无力场模型(Global Linear Force-Free Field,GLFFF)进行磁场外推,分析日冕物质抛射偏转与背景磁场能量密度分布之间的关系,并计算日冕物质抛射的运动轨迹。通过改变无力因子α,发现当α=0.15时,计算得到的日冕物质抛射运动轨迹与实际观测的日冕物质抛射运动轨迹拟合得最好。

Coronal Mass Ejection（ CME） is the process that huge amount of foamy gas which carries the magnetic field lines,is projected from the sun in a few hours. CME releases high levels of radiation and a large number of charged particles which will cause great disturbances to the Sun-Earth magnetic field when they travel to the vicinity of the Earth. CME is the driven source of the geomagnetic storms and moderate solar energetic particle events. The change of CME propagation direction determines whether a CME could arrive on Earth. Therefore,to study the deflection of CME could offer a better understanding about its affections to space weather,which is significant to predict space weather events. This paper analyzes the deflection data of CME observed by STEREO satellite on the 8 October 2007. It uses the Global Linear Force-Free Field model to extrapolate magnetic field and analyzes the relationship between the distribution of the background magnetic energy density and the deflection of CME. The trajectory of CME is calculated. The result shows that the theoretical trajectory of CME fit the actual observations most closely when the force free parameter α = 0. 15.