Transverse oscillations of coronal loops

几十年来，人们已经知道太阳大气具有很强的磁性结构。其中一个主要的磁性结构是日冕环。这些环是在日冕磁场方向上拉长的结构，其特征是等离子体的密度和温度增加。1998年，TRACE首次观测到这些结构在横向上的振荡，这是由外部扰动引起的（很可能是由太阳耀斑引起的）。此后，日冕环横向振荡现象引起了太阳物理学家的广泛关注。横向振荡特别重要，因为它们是日冕地震学或太阳磁地震学这一太阳物理学新兴分支的主要研究对象。日冕地震学的主要思想是通过观测日冕的波动和振荡来获得有关日冕等离子体和磁场参数的信息。横向日冕环振荡已被用来估计：(1)日冕环中的磁场强度；（ii）日冕的大气尺度高度。为了在这类估计中达到足够的精度，非常需要一个完善的横向日冕环振荡理论。该理论的主要目标是将在地震学应用中重要的日冕环参数与那些不重要的、因此可以忽略的参数区分开来。近年来，在这方面已经取得了初步但至关重要的进展。例如，在当前和近期仪器分辨率水平上，已经表明密度和沿环截面半径的变化是非常重要的，而环曲率和磁扭则不太重要。然而，关于横向日冕环振荡的理论还远远不够完善。为了获得亚分辨率诊断信息，需要开发新的和更复杂的模型。其中主要的理论挑战是发展横向日冕环振荡的非线性理论，以及由几个日冕环组成的系统的集体振荡理论。我们的项目解决了这些关键的高级问题。

It has been known for a few decades that the solar atmosphere is strongly magnetically structured. One of the main magnetic structures are the coronal loops. These loops are the structures elongated in the magnetic field direction in the solar corona that are characterized by the enhanced density and temperature of the plasma. In 1998 TRACE observed first oscillations of these structures in the transverse direction caused by an external perturbation (most probably generated by a solar flare). After that the phenomenon of transverse coronal loop oscillations received an ample attention of solar physicists. Transverse oscillations are especially important because they are the key objects of studies in the new and fast emerging branch of solar physics called coronal seismology or solar magneto-seismology. The main idea of coronal seismology is to obtain information about parameters of the coronal plasma and magnetic field from observations of waves and oscillations taking place in the solar corona. The transverse coronal loop oscillations have been used to estimate: (i) The magnetic field magnitude in coronal loops; (ii) The atmospheric scale height in the solar corona. To achieve sufficient accuracy in the estimates of this type a well-developed theory of transverse coronal loop oscillations is much needed. The main goal of this theory is to separate coronal loop parameters that are important in seismological applications from those that are not important, and thus can be neglected. Initial but vital progress has already been made in this direction in the recent years. For example, it has been shown that the variation of the density and cross-section radius along the loop are very important, while loop curvature and the magnetic twist are less important at the level of present and near-future instrumental resolution. However, the theory of transverse coronal loop oscillations is far from being complete. New and more sophisticated models are to be developed in order to obtain sub-resolution diagnostic informations. Among the main theoretical challenges are the development of nonlinear theory of transverse coronal loop oscillations, and the theory of collective oscillations of a system of a few coronal loops. Our project addresses these crucial advanced problems.