Forbush在CME前沿降低和turbulence水平
Forbush decreases and turbulence levels at CME fronts
摘要:
我们试图估计日冕物质抛射(CME)锋面附近的MHD湍流的平均水平,因为它们从太阳传播到地球。我们研究了宇宙射线数据的GRAPES-3跟踪μ子望远镜在Ooty,连同其他来源的数据,以及观察到的福布什减少事件。这些事件中的每一个都与正面晕日冕物质抛射(CME)和近地磁云有关。在每一种情况下,我们估计的福布什减少的幅度使用一个简单的模型,通过封闭的大部分场线包围日冕物质抛射,因为它的扩展和传播从太阳到地球的高能量质子的扩散。我们使用的跨场扩散系数$D_{\perp}$的估计来自广泛的蒙特卡罗模拟的宇宙射线通过湍流磁场传播的出版结果。我们的方法有助于限制在湍流磁场的能量密度的比值,在平均磁场附近的日冕物质抛射锋。对于2001年4月11日的福布什减少事件,发现该比率为$\sim$ 2%,对于2003年11月20日的福布什减少事件,发现该比率为$\sim$ 6%,而对于2003年10月29日的更高能量的事件,发现该比率为$\sim$ 249%。
英文摘要:
We seek to estimate the average level of MHD turbulence near coronal mass ejection (CME) fronts as they propagate from the Sun to the Earth. We examine the cosmic ray data from the GRAPES-3 tracking muon telescope at Ooty, together with the data from other sources for three well observed Forbush decrease events. Each of these events are associated with frontside halo Coronal Mass Ejections (CMEs) and near-Earth magnetic clouds. In each case, we estimate the magnitude of the Forbush decrease using a simple model for the diffusion of high energy protons through the largely closed field lines enclosing the CME as it expands and propagates from the Sun to the Earth. We use estimates of the cross-field diffusion coefficient $D_{\perp}$ derived from published results of extensive Monte Carlo simulations of cosmic rays propagating through turbulent magnetic fields. Our method helps constrain the ratio of energy density in the turbulent magnetic fields to that in the mean magnetic fields near the CME fronts. This ratio is found to be $\sim$ 2% for the 11 April 2001 Forbush decrease event, $\sim$ 6% for the 20 November 2003 Forbush decrease event and $\sim$ 249% for the much more energetic event of 29 October 2003.
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