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arXiv 1303.3299astro-ph.SR
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磁场在耀斑大气加热驱动的瞬态地震辐射中的作用

The Role of Magnetic Fields in Transient Seismic Emission Driven by Atmospheric Heating in Flares

C. Lindsey, A. -C. Donea, J. C. Martinez Oliveros, H. S. Hudson

摘要:

耀斑中的瞬态地震辐射的物理学在很大程度上仍然是个谜。它的发现者提出,这些“日震”是由耀斑色球层的“厚目标加热”驱动的冲击的特征。H-α观测显示了这种冲击的证据。然而,对脉冲色球加热驱动的冲击的模拟显示,随着冲击的向下进行,辐射损失逐渐减少。受冲击气体的压缩加热并增加其密度,使其更具辐射性。因此,辐射损失随着冲击的强度急剧增加。这引起了怀疑,从这样的冲击足够的能量可以渗透到太阳内部,以匹配所显示的日震签名。我们指出,由脉冲加热驱动的声学瞬变的模拟没有考虑瞬态震源环境的磁场特性。这对传导到太阳内部的地震通量一定有重大影响。例如,一个强的水平磁场会大大增加色球介质的压缩模量。这大大减少了气体的压缩,从而减少了瞬变通过时的辐射损失,这可以解释震源与强的、高度倾斜的半影磁场区域的强烈亲和力。因此,倾斜磁场的作用对于我们理解脉冲加热在瞬态地震辐射中的作用至关重要。

英文摘要:

The physics of transient seismic emission in flares remains largely mysterious. Its discoverers proposed that these "sunquakes" are the signature of a shock driven by "thick-target heating" of the flaring chromosphere. H-α observations show evidence for such a shock. However, simulations of shocks driven by impulsive chromospheric heating show withering radiative losses as the shock proceeds downward. The compression of the shocked gas heats and increases its density, making it more radiative. So, radiative losses increase radically with the strength of the shock. This has introduced doubt that sufficient energy from such a shock can penetrate into the solar interior to match that indicated by the helioseismic signatures. We point out that simulations of acoustic transients driven by impulsive heating have no account for magnetic fields characteristic of transient-seismic-source environments. These must have a major impact on the seismic flux conducted into the solar interior. A strong horizontal magnetic field, for example, greatly increases the compressional modulus of the chromospheric medium. This greatly reduces compression of the gas, hence the radiative losses as the transient passes through it. This could explain the strong affinity of seismic sources to regions of strong, highly inclined penumbral magnetic fields. The role of inclined magnetic fields, then, is fundamental to our understanding of the role of impulsive heating in transient seismic emission.

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