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arXiv 1006.3473astro-ph.SRphysics.plasm-phphysics.space-ph
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冕洞中Alfven波Turbulence和垂直离子温度

Alfven Wave Turbulence and Perpendicular Ion Temperatures in Coronal Holes

Benjamin D. G. Chandran

摘要:

当湍流振幅足够大时,低频阿尔芬波湍流导致离子轨迹变得混乱或“随机”。随机轨道使离子能够从湍流中吸收能量,即使当波动频率太小而无法发生回旋共振时,也会增加垂直离子温度。在本文中,一个解析表达式的随机加热率结合观测约束湍流模型得到的解析公式的垂直离子温度作为日心距离r,离子质量和离子电荷的函数在冕洞的r值之间的2和15太阳半径(Rs)。得到的温度分布提供了一个很好的适合质子和OVI离子在2Rs < r < 3Rs的紫外电晕光谱仪(UNOPS)的观察。随机加热也提供了一个自然的解释几个详细的特征的UVI观测,包括优先和各向异性加热的次要离子,快速径向增加的OVI温度之间的1.6 Rs和1.9 Rs,和突然平坦的OVI温度曲线r增加超过1.9 Rs。

英文摘要:

Low-frequency Alfven-wave turbulence causes ion trajectories to become chaotic, or "stochastic," when the turbulence amplitude is sufficiently large. Stochastic orbits enable ions to absorb energy from the turbulence, increasing the perpendicular ion temperature even when the fluctuation frequencies are too small for a cyclotron resonance to occur. In this paper, an analytic expression for the stochastic heating rate is used in conjunction with an observationally constrained turbulence model to obtain an analytic formula for the perpendicular ion temperature as a function of heliocentric distance r, ion mass, and ion charge in coronal holes for values of r between 2 and 15 solar radii (Rs). The resulting temperature profiles provide a good fit to observations of protons and OVI ions at 2Rs < r < 3Rs from the Ultraviolet Coronagraph Spectrometer (UVCS). Stochastic heating also offers a natural explanation for several detailed features of the UVCS observations, including the preferential and anisotropic heating of minor ions, the rapid radial increase in the OVI temperature between 1.6Rs and 1.9Rs, and the abrupt flattening of the OVI temperature profile as r increases above 1.9Rs.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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