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arXiv 1507.04375astro-ph.SR
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太阳耀斑和恒星耀斑的统一计算模型

A Unified Computational Model for Solar and Stellar Flares

Joel C. Allred, Adam F. Kowalski, Mats Carlsson

摘要:

我们提出了一个统一的计算框架,可用于描述太阳和dMe星上的脉冲耀斑。这些模型假设耀斑脉冲相是由一束带电粒子引起的,带电粒子在日冕中加速并向下传播,沿途沉积能量和动量。这迅速加热了较低的恒星大气层,使其爆炸性膨胀并显着变亮。我们的模型包括从次光球延伸到日冕的通量管。利用Fokker-Planck动力学理论模拟了耀斑加速的带电粒子沿一维流管传播并加热恒星大气的过程。详细的辐射转移包括在内,使模型预测可以直接与观测进行比较。耀斑加速粒子的通量驱动返回电流,从而额外加热恒星大气。这些影响也包括在我们的模型中。我们研究模型太阳和dMe恒星大气的耀斑加速粒子束的影响,并进行参数研究不同的注入粒子能谱。我们发现大气响应强烈地依赖于加速粒子截止能量和光谱指数。

英文摘要:

We present a unified computational framework which can be used to describe impulsive flares on the Sun and on dMe stars. The models assume that the flare impulsive phase is caused by a beam of charged particles that is accelerated in the corona and propagates downward depositing energy and momentum along the way. This rapidly heats the lower stellar atmosphere causing it to explosively expand and dramatically brighten. Our models consist of flux tubes that extend from the sub-photosphere into the corona. We simulate how flare-accelerated charged particles propagate down one-dimensional flux tubes and heat the stellar atmosphere using the Fokker-Planck kinetic theory. Detailed radiative transfer is included so that model predictions can be directly compared with observations. The flux of flare-accelerated particles drives return currents which additionally heat the stellar atmosphere. These effects are also included in our models. We examine the impact of the flare-accelerated particle beams on model solar and dMe stellar atmospheres and perform parameter studies varying the injected particle energy spectra. We find the atmospheric response is strongly dependent on the accelerated particle cutoff energy and spectral index.

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