KINETIC INSTABILITY OF DRIFT-ALFVÉN WAVES IN SOLAR CORONA AND STOCHASTIC HEATING
KINETIC INSTABILITY OF DRIFT-ALFVÉN WAVES IN SOLAR CORONA AND STOCHASTIC HEATING
复制标题
日冕和随机加热中漂移阿尔文波的动力学不稳定性
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
S. Poedts
中科院分区：
文献类型：
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作者：
J. Vranjes;S. Poedts
无论在水平方向还是垂直方向上，太阳大气都是有结构且不均匀的。日冕磁环的无所不在意味着平衡等离子体数量的梯度，如密度、磁场和温度。这些梯度负责激发漂移波，这些漂移波在双分量流体描述中（在存在碰撞和没有碰撞的情况下）和在双分量动力学描述中（由于纯粹的动力学效应）增长。在这项工作中，密度梯度在垂直于磁场矢量方向上的影响在动力学理论中进行了研究，在静电（ES）和电磁（EM）制度。EM状态意味着梯度驱动漂移波与alfvsamn波的耦合。对两种情况下的增长率进行了计算和比较。研究发现，一般来说，与EM扰动相比，ES体系具有更强的增长率。文中还讨论了漂移波的随机加热问题。由于这种加热而释放的能量密度应该更多地依赖于背景磁场的大小，而不是漂移波和阿尔夫沙曼波的耦合。在磁场较强的地区，预计随机加热要高得多。总的来说，随机加热引起的能量释放率可能比目前公认的持续日冕加热所必需的值高出几个数量级。垂直分层和沿磁环的超长波长意味着，沿磁环以扭曲结构传播的漂移- alfv<s:1>波浪实际上占据了具有不同等离子体-β的区域，因此可能具有不同的（EM-ES）特性，导致在一两个波长内的不同加热速率。
The solar atmosphere is structured and inhomogeneous, both horizontally and vertically. The omnipresence of coronal magnetic loops implies gradients of the equilibrium plasma quantities such as the density, magnetic field, and temperature. These gradients are responsible for the excitation of drift waves that grow both within the two-component fluid description (both in the presence of collisions and without it) and within the two-component kinetic descriptions (due to purely kinetic effects). In this work, the effects of the density gradient in the direction perpendicular to the magnetic field vector are investigated within the kinetic theory, in both electrostatic (ES) and electromagnetic (EM) regimes. The EM regime implies the coupling of the gradient-driven drift wave with the Alfvén wave. The growth rates for the two cases are calculated and compared. It is found that, in general, the ES regime is characterized by stronger growth rates, as compared with the EM perturbations. Also discussed is the stochastic heating associated with the drift wave. The released amount of energy density due to this heating should be more dependent on the magnitude of the background magnetic field than on the coupling of the drift and Alfvén waves. The stochastic heating is expected to be much higher in regions with a stronger magnetic field. On the whole, the energy release rate caused by the stochastic heating can be several orders of magnitude above the value presently accepted as necessary for a sustainable coronal heating. The vertical stratification and the very long wavelengths along the magnetic loops imply that a drift-Alfvén wave, propagating as a twisted structure along the loop, in fact occupies regions with different plasma-β and, therefore, may have different (EM–ES) properties, resulting in different heating rates within just one or two wavelengths.