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arXiv 1006.4337astro-ph.SR
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1997年5月12日CME事件的数值模拟--磁重联的作用

Numerical Simulation of the May 12, 1997 CME Event - the Role of Magnetic Reconnection

O. Cohen, G. D. R. Attrill, N. A. Schwadron, N. U. Crooker, M. J. Owens, C. Downs, T. I. Gombosi

摘要:

利用日冕磁流体动力学(MHD)模型,对1997年5月12日发生的日冕物质抛射(CME)及其与日冕磁场的相互作用进行了数值研究。环境太阳风稳态解是由光球磁场数据驱动的,而太阳爆发是通过在稳态解上叠加一个不稳定的通量绳得到的。在日冕物质抛射的初始阶段,核心磁绳与邻近的磁场重新连接,这有利于日冕物质抛射在低日冕中的横向扩展。磁通绳场也以击穿模型的方式与相反取向的上覆磁场重新连接。在这一阶段的喷发,模拟的日冕物质抛射逆时针旋转,以实现一个方向,这是在协议的行星际通量绳在1天文单位观察。日冕物质抛射的一个重要组成部分是扩展到行星际空间的,它包括一个旁瓣,主要是由于与覆盖场重连而产生的。在3小时内,重连有效地修改了CME的连接性,从最初的两个足点都扎根在活动区的情况下,一个足点被转移到安静的太阳,在一个显着的距离($\approx 1R_\odot$)从原来的源区。当日冕物质抛射到达盔状流带的外缘时,由于与上覆的磁场相互作用而引起的膨胀和旋转停止,在盔状流带处,磁场在全球范围内组织起来。因此,模拟提供了一个新的观点的作用重联旋转的CME通量绳和运输的足迹,同时保持其核心结构。

英文摘要:

We perform a numerical study of the evolution of a Coronal Mass Ejection (CME) and its interaction with the coronal magnetic field based on the May 12, 1997, CME event using a global MagnetoHydroDynamic (MHD) model for the solar corona. The ambient solar wind steady-state solution is driven by photospheric magnetic field data, while the solar eruption is obtained by superimposing an unstable flux rope onto the steady-state solution. During the initial stage of CME expansion, the core flux rope reconnects with the neighboring field, which facilitates lateral expansion of the CME footprint in the low corona. The flux rope field also reconnects with the oppositely orientated overlying magnetic field in the manner of the breakout model. During this stage of the eruption, the simulated CME rotates counter-clockwise to achieve an orientation that is in agreement with the interplanetary flux rope observed at 1 AU. A significant component of the CME that expands into interplanetary space comprises one of the side lobes created mainly as a result of reconnection with the overlying field. Within 3 hours, reconnection effectively modifies the CME connectivity from the initial condition where both footpoints are rooted in the active region to a situation where one footpoint is displaced into the quiet Sun, at a significant distance ($\approx 1R_\odot$) from the original source region. The expansion and rotation due to interaction with the overlying magnetic field stops when the CME reaches the outer edge of the helmet streamer belt, where the field is organized on a global scale. The simulation thus offers a new view of the role reconnection plays in rotating a CME flux rope and transporting its footpoints while preserving its core structure.

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