Coronal heating and the importance of MHD waves

太阳为我们提供了许多有趣的谜题。一个令人惊讶的结果是，太阳光球层比上面的日冕温度低100倍。日冕的加热机制与太阳磁场有关，但将能量从太阳内部传输到日冕并储存在那里的确切物理过程尚不清楚。有几种可能性，但没有一种真正从理论上得到证明。这个项目将检验一种新的自洽日冕加热模型。它将研究缓慢积累的磁应力如何产生等离子体不均匀，从而帮助短周期波有效地衰减。这个项目将使用数值方法和现有的程序来求解控制太阳等离子体过程的MHD方程，并将确定波中是否有足够的能量将日冕等离子体维持在100万度。数值模拟的优点是可以包含正确的日冕热力学，以便可以将等离子体的温度和密度与当前的观测结果进行比较。背景和需要解决的关键问题已经提出了各种加热机制，传统上，它们分为两大类，即波加热和磁重联加热。通过重新连接来加热需要在一段时间内缓慢地存储太阳日冕中的磁能，因为表面的缓慢运动不断地对磁场施加压力。然后，通过触发磁重联，这些存储的能量被迅速释放。触发事件可能导致随后的能量释放事件的雪崩(Hood等人，Asterphys J，817,2016)。波加热假定加热日冕所需的能量通过波传输到那里。这些低幅度波具有比存储方法的慢时间刻度快得多的短周期。本项目将结合慢应力运动来研究波加热机制。

AbstractThe Sun provides us with many interesting puzzles. One surprising result is that the solar photosphere is 100 times cooler than the overlying corona. The mechanism that heats the corona is related to the Sun's magnetic field but the exact physical process that transports energy from the solar interior up to the corona and deposits it there remains unknown. There are several possibilities but none have really been demonstrated theoretically.This project will examine a new self-consistent coronal heating model. It will investigate how a slow build-up of magnetic stresses can create the plasma inhomogeneities that can help short period waves damp efficiently. This project will solve the MHD equations, which govern plasma processes in the Sun, using numerical methods and an existing program, and will determine whether there is enough energy in the waves to maintain a coronal plasma at 1 million degrees. The advantage of the numerical modelling is that the correct coronal thermodynamics can be included so that the temperature and density of the plasma can be compared with current observations.Background and key issues to be addressedThere are various heating mechanisms that have been proposed and, traditionally, they have been split into two main categories, namely heating by waves and heating by magnetic reconnection. Heating by reconnection requires the slow storage of magnetic energy in the solar corona over a period of time as slow motions at the surface continually stress the magnetic field. This stored energy is then released rapidly through the triggering of magnetic reconnection. The triggering event can cause a subsequent avalanche of energy release events (Hood et al, Astrophys J, 817, 2016). Heating by waves assumes that the energy required to heat the corona is transported there by waves. These low amplitude waves have a short period that is much faster than the slow timescale for the storage method. This project will investigate wave heating mechanisms in combination with the slow stressing motions