Heating by transverse waves in simulated coronal loops
Heating by transverse waves in simulated coronal loops
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DOI：
10.1051/0004-6361/201730598
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发表时间：
2017-06
期刊：
影响因子：
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通讯作者：
K. Karampelas;T. Doorsselaere;P. Antolin
中科院分区：
文献类型：
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作者：
K. Karampelas;T. Doorsselaere;P. Antolin
最近对振荡通量管的数值研究证实了共振吸收在阻尼冕环中传播的横向振荡中的重要意义。与开尔文-亥姆霍兹不稳定性一起考察了该机制的非线性性质，开尔文-亥姆霍兹不稳定性预计将在通量管边缘的共振层中表现出来。虽然这两个过程被假设为通过将波能耗散到更小的尺度来加热日冕环路，但与更热的环境发生的混合可能会隐藏这种影响。我们的目的是研究日冕环中驱动扭结波和驻留扭结波对波加热的影响。使用MPI-AMRVAC程序，我们对(A)脚点驱动和(B)直日冕通量管中的自由驻留振荡进行了理想的三维磁流体力学(MHD)模拟。我们观察到了这三种模式在环边界层上开尔文-亥姆霍兹涡的发展，以及环内体积平均温度的增加。我们的设置中的主要加热机制是欧姆耗散，这一点从脚点附近较高的温度和电流密度值可以看出。内管和周围等离子体之间的温度梯度的引入表明，在较热的环境中，这两个区域的混合大大提高了最强湍流位置处的管内温度，这超出了上述波加热机制的贡献。
Recent numerical studies of oscillating flux tubes have established the significance of resonant absorption in the damping of propagating transverse oscillations in coronal loops. The nonlinear nature of the mechanism has been examined alongside the Kelvin-Helmholtz instability, which is expected to manifest in the resonant layers at the edges of the flux tubes. While these two processes have been hypothesized to heat coronal loops through the dissipation of wave energy into smaller scales, the occurring mixing with the hotter surroundings can potentially hide this effect. We aim to study the effects of wave heating from driven and standing kink waves in a coronal loop. Using the MPI-AMRVAC code, we perform ideal, three dimensional magnetohydrodynamic (MHD) simulations of both (a) footpoint driven and (b) free standing oscillations in a straight coronal flux tube, in the presence of numerical resistivity. We have observed the development of Kelvin-Helmholtz eddies at the loop boundary layer of all three models considered here, as well as an increase of the volume averaged temperature inside the loop. The main heating mechanism in our setups was Ohmic dissipation, as indicated by the higher values for the temperatures and current densities located near the footpoints. The introduction of a temperature gradient between the inner tube and the surrounding plasma, suggests that the mixing of the two regions, in the case of hotter environment, greatly increases the temperature of the tube at the site of the strongest turbulence, beyond the contribution of the aforementioned wave heating mechanism.