行星际日冕物质抛射引起福布斯下降的一维随机微分模拟

发布时间：2018-08-23 12:07

【摘要】：福布斯下降(Forbush decrease,FD)是银河宇宙线(galactic cosmic rays,GCRs)受短期剧烈太阳活动调制的重要现象之一.本文设GCRs进入由行星际日冕物质抛射(interplanetary coronal mass ejection,ICME)及其前沿激波共同形成的扰动区时,其径向扩散系数κ_(rr)受抑制变为μ(r)·κ_(rr)(0μ(r)1),且抑制强度与粒子位置处的太阳风等离子体速度正相关.对任意时刻的扰动区,抑制系数μ(r)在激波处最小为μ(r_(sh)),并按指数规律增大,在ICME尾部归一.CME爆发时,μ(r_(sh))取全局最小值μm.在扰动区向日球层外传播的过程中,μ(r_(sh))逐步恢复为1.在此基础上,根据GOES和ACE卫星观测确定模型参数,用一维随机微分方程描述GCRs在日球层内的传播,并采用倒向随机方法模拟了一个由独立Halo ICME调制GCRs引起的2005年5月15日FD事件.计算所得地面中子通量的主相、恢复相及其在CME到达地球前的增加过程,均与Oulu中子探测器观测结果一致.
[Abstract]:Forbush decline (FD) is one of the most important phenomena of galactic cosmic ray (galactic cosmic) which is modulated by short term intense solar activity. In this paper, let the radial diffusion coefficient 魏 _ (rr) be reduced to 渭 (r) 魏 _ (rr) (0 渭 (r) _ 1 when GCRs enters the disturbed region formed by the interplanetary coronal mass ejection (ICME) and its front shock waves, and the inhibitory intensity is positively correlated with the solar wind plasma velocity at the position of the particle. For the disturbance region at any time, the suppression coefficient 渭 (r) is minimum 渭 (r _ (sh),) at the shock wave and increases exponentially, and 渭 (r _ (sh) takes the global minimum value 渭 (r _ (sh) when the ICME tail is normalized. 渭 (r _ (sh) gradually recovered to 1. 1 as the disturbance region propagated to the outer heliosphere. Based on the model parameters determined by GOES and ACE satellite observations, one-dimensional stochastic differential equations are used to describe the propagation of GCRs in the heliosphere. A FD event of May 15, 2005 caused by an independent Halo ICME modulated GCRs is simulated by backward random method. The calculated surface neutron flux in the main phase, the recovery phase and the increasing process before CME reaches the earth are in agreement with the observed results of the Oulu neutron detector.
【作者单位】：南京信息工程大学物理系;南京信息工程大学空间天气研究所;
【分类号】：P182

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