Current Sheet Equilibria and Disruptions

在本提案中，我们将讨论亚暴期间局部和全局磁自由能转换为粒子动能的物理问题。对这些过程的理解将对全球磁层对太阳风变化的响应具有重要意义。例如，这可能会导致理解亚暴释放的自由能在尾巴上损失的能量和对内部磁层和电离层所做的功之间的分配。此外，这种关于亚暴期间储存的磁能的全球释放的理论可能对其他空间物理学和天体物理学背景下的能量释放现象具有重要意义。目前提出的研究与过去类似研究的不同之处在于，我们的研究将基于局部电流中断的电流片突变模型（c.f. Lui et al., 1988）。该模型来源于非零Ey和非零Bz的一维电流片构型的时间无关和时间相关计算。Burkhart等，1992a；Pritchett and Coroniti, 1993；Burkhart et al., 1993。在这些计算中发现，在边界条件的准静态演化下，产生了一种力的不平衡，我们称之为流板突变。随后的时间发展导致电流片在一段时间间隔内的湍流破坏，并将相关的磁场能量转换为粒子能量。在提出的研究中，我们将对各种初始条件和边界条件进行ID计算，以确定当前薄片突变特征的鲁棒性和缩放性。我们将在二维时间相关的混合代码中研究电流中断的径向扩展，对于第一个切割，使用与x无关的初始平衡。我们将扩展一维平衡计算，包括x依赖，我们将研究活动的扩展和相应的局部和全局转换磁场能量到等离子体能量使用x依赖的初始平衡在时间依赖，混合模拟代码。

In this proposal, we will address the physics of local and global conversion of magnetic free energy to particle kinetic energy during substorms. An understanding of these processes will be important implications to the global response of the magnetosphere to solar wind variations. For example, this could lead to an understanding of the partitioning of substorm released free energy between energy lost down the tail and work done on the inner magnetosphere and ionosphere. Also, such a theory of the global release of stored magnetic energy during substorms could have important implications for energy release phenomena in other space physics and astrophysical contexts. The difference between the presently proposed study and similar studies of the past is that our study will be based upon the current sheet catastrophe model for local current disruption c.f. Lui et al., 1988 . This model arises from time independent and time dependent calculations of 1D current sheet configurations with a nonzero Ey and nonzero Bz Burkhart et al., 1992a; Pritchett and Coroniti, 1993; Burkhart et al., 1993 . It was found in these calculations that under the quasi-static evolution of the boundary conditions a force imbalance, which we have called the current sheet catastrophe, develops. Subsequent time development leads to the turbulent destruction of the current sheet over some time interval and the conversion of the associated magnetic field energy to particle energy. In the proposed research, we shall perform ID calculations for a variety of initial conditions and boundary conditions to determine the robustness and scaling of the signatures of the current sheet catastrophe. We shall study the radial expansion of current disruption in a 2D, time-dependent, hybrid code, using, for the first cut, x-independent initial equilibria. We shall extend the 1D equilibrium calculations to include x-dependence and we shall study the expansion of activity and the corresponding local and global conversion of magnetic field energy to plasma energy using the x-dependent initial equilibria in a time-dependent, hybrid simulation code.