Three-Dimensional Magnetohydrodynamic Simulation of Nonlinear Magnetic Buoyancy Instability of Flux Sheets with Magnetic Shear
Three-Dimensional Magnetohydrodynamic Simulation of Nonlinear Magnetic Buoyancy Instability of Flux Sheets with Magnetic Shear
复制标题
磁剪磁通片非线性磁浮力不稳定性的三维磁流体动力学模拟
DOI：
10.1093/pasj/57.6.995
复制
发表时间：
2005
影响因子：
2.3
通讯作者：
S. Nozawa
中科院分区：
文献类型：
--
作者：
S. Nozawa
采用三维磁流体力学数值模拟方法，研究了具有磁剪切力的磁通片的磁浮力不稳定性的非线性演化过程。初始位于太阳光球层下方的水平通量片对交换不稳定性和帕克不稳定性(磁浮力不稳定性的起伏模式)都很敏感。数值模拟中失稳的线性阶段的增长率与线性理论预测的一致。在非线性阶段，发展依赖于初始扰动和初始磁场构型(即磁切变的存在)。当初始扰动被假定为周期性时，浮现的磁通上升到日冕，磁场像势场一样扩展，正如在2D模拟中所观察到的那样。当假定初始的非周期扰动或随机扰动时，当磁场稍微进入光球层时，磁通量水平扩展。磁场和气体的分布趋于一种新的磁流体静力平衡状态。当初始磁通片中存在磁切变时，交换模式稳定，从而出现的回路比无磁切变情况下的高。我们讨论了所给出的结果与在太阳上观测到的新兴通量之间的关系。
A series of three-dimensional magnetohydrodynamic simulations is used to study the nonlinear evolution of the magnetic buoyancy instability of a magnetic flux sheet with magnetic shear. A horizontal flux sheet that is initially placed below the solar photosphere is susceptible to both the interchange instability and the Parker instability (the undular mode of the magnetic buoyancy instability). The growth rate in the linear stage of the instability in the numerical simulation is consistent with that predicted by linear theory. In the nonlinear stage, the development depends on the initial perturbation as well as the initial magnetic field configuration (i.e., the presence of magnetic shear). When an initial perturbation is assumed to be periodic, the emerging flux rises to the corona and the magnetic field expands like a potential field, as observed in 2D simulations. When an initial non-periodic perturbation or random perturbations are assumed, the magnetic flux expands horizontally when the magnetic field emerges a little into the photosphere. The distribution of the magnetic field and gas tends to be in a new state of magnetohydrostatic equilibrium. When magnetic shear is present in the initial magnetic flux sheets, the interchange mode is stabilized so that the emerging loop is higher than in the no magnetic shear case. We discuss how the presented results are related to the emerging flux observed on the Sun.