通过部分电离太阳大气的通量管的出现
Emergence of a flux tube through a partially ionised solar atmosphere
摘要：
对于一个磁通量管，或者说任何一个磁通量，要从对流区进入日冕，它必须穿过低层大气的部分电离层：光球层和色球层。在这样的区域中，离子-中性碰撞导致流过磁场线的电流的电阻率增加。该Cowling电阻率可以超过Spitzer电阻率几个数量级，并且在2.5D模拟中已经显示出足以从出现的通量中去除所有交叉场电流。在这里，我们将这种建模扩展到3D。再一次发现，考林电阻率去除垂直电流。然而，3D结构的存在阻止了2.5D模拟中可能的简单比较。在完全电离的大气中，通量的出现导致了上覆日冕中的非物理低温区域，色球层物质的提升以及随后的瑞利-泰勒不稳定性的发生。包括中性粒子消除了低温区域，提升了更少的色球物质，并且没有瑞利-泰勒不稳定性的迹象。因此，磁通出现的模拟应该包括这样的中性层，以获得正确的垂直电流，消除瑞利-泰勒不稳定性，并获得正确的温度分布。在温度并不重要的情况下，即当没有模拟的光谱发射是必需的，一个简单的中性层模型证明充分再现完全一致的模拟结果。
英文摘要：
For a magnetic flux tube, or indeed any flux, to emerge into the Solar corona from the convection zone it must pass through the partially ionised layers of the lower atmosphere: the photosphere and the chromosphere. In such regions the ion-neutral collisions lead to an increased resistivity for currents flowing across magnetic field lines. This Cowling resistivity can exceed the Spitzer resistivity by orders of magnitude and in 2.5D simulations has been shown to be sufficient to remove all cross field current from emerging flux. Here we extend this modelling into 3D. Once again it is found that the Cowling resistivity removes perpendicular current. However the presence of 3D structure prevents the simple comparison possible in 2.5D simulations. With a fully ionised atmosphere the flux emergence leads to an unphysically low temperature region in the overlying corona, lifting of chromospheric material and the subsequent onset of the Rayleigh-Taylor instability. Including neutrals removes the low temperature region, lifts less chromospheric matter and shows no signs of the Rayleigh-Taylor instability. Simulations of flux emergence therefore should include such a neutral layer in order to obtain the correct perpendicular current, remove the Rayleigh-Taylor instability and get the correct temperature profile. In situations when the temperature is not important, i.e. when no simulated spectral emission is required, a simple model for the neutral layer is demonstrated to adequately reproduce the results of fully consistent simulations.
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