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arXiv 1104.2298astro-ph.SRphysics.plasm-ph
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SOHO观测到的日冕物质抛射过程中的等离子体加热

Plasma Heating During a Coronal Mass Ejection Observed by SOHO

N. A. Murphy, J. C. Raymond, K. E. Korreck

摘要:

我们进行了一个时间依赖的电离分析,以限制等离子体加热的要求,在快速部分晕日冕物质抛射(CME)观察到的2000年6月28日的紫外日冕光谱仪(UNOPS)的太阳和日光层天文台(SOHO)。我们用两种方法从UNOPS的测量中得到密度,包括在1213.85和1218.35埃处的密度敏感的O-V线比,以及色球发射线对O-VI 1032,1038双重态的辐射泵浦。最强约束的特征显示累积等离子体加热与动能相当或更大,而在事件期间较早观察到的特征显示累积等离子体加热的量级或小于动能。利用SOHO迈克尔逊多普勒成像仪(MDI)观测资料估算了活动区的磁场能量。我们考虑候选等离子体加热机制,并在可能的情况下提供约束。由于这次CME与相对较弱的耀斑有关,耀斑能量的贡献(例如,通过热传导或高能粒子)可能很小;然而,耀斑可能部分位于边缘之后。由光球运动产生的波加热需要的加热速率比以前对冕洞的推断要大得多,但是喷发本身可以驱动加热等离子体的波。在磁通绳或CME电流片的小规模重联加热没有显着的约束。不稳定谱线的宽度表明,湍流必须不断补充和消散的时间尺度短于传播时间,以便在CME加热的中间步骤。

英文摘要:

We perform a time-dependent ionization analysis to constrain plasma heating requirements during a fast partial halo coronal mass ejection (CME) observed on 2000 June 28 by the Ultraviolet Coronagraph Spectrometer (UVCS) aboard the Solar and Heliospheric Observatory (SOHO). We use two methods to derive densities from the UVCS measurements, including a density sensitive O V line ratio at 1213.85 and 1218.35 Angstroms, and radiative pumping of the O VI 1032,1038 doublet by chromospheric emission lines. The most strongly constrained feature shows cumulative plasma heating comparable to or greater than the kinetic energy, while features observed earlier during the event show cumulative plasma heating of order or less than the kinetic energy. SOHO Michelson Doppler Imager (MDI) observations are used to estimate the active region magnetic energy. We consider candidate plasma heating mechanisms and provide constraints when possible. Because this CME was associated with a relatively weak flare, the contribution by flare energy (e.g., through thermal conduction or energetic particles) is probably small; however, the flare may have been partially behind the limb. Wave heating by photospheric motions requires heating rates significantly larger than those previously inferred for coronal holes, but the eruption itself could drive waves which heat the plasma. Heating by small-scale reconnection in the flux rope or by the CME current sheet is not significantly constrained. UVCS line widths suggest that turbulence must be replenished continually and dissipated on time scales shorter than the propagation time in order to be an intermediate step in CME heating.

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