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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Auroral arcs as current transformers
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Auroral arcs as current transformers

机译：极光弧电流互感器

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摘要

We treat the effects of an electric field tangential to an auroral arc on the basis of an analytical model according to which auroral arcs are energized by the release of magnetic shear stresses and associated internal energy (Haerendel, 2007). If the tangential field exceeds a certain (low) threshold, the ionosphere acts as a current generator, or better transformer, and the magnetosphere as the load. The reason is that energy supplied by a longitudinal Type I current system, as defined by Bostr?m in 1964, is transformed into energy of the latitudinal Type II current system attached to the arc and is mostly consumed by the auroral acceleration process. Closure of the transformer current in the upper magnetosphere and energy deposition in form of internal energy and shear stresses, although small, are crucial for the operation of this process. It can be visualized as a dragging of magnetic field and plasma along the arc in the direction of higher magnetospheric pressure enforced by the electric polarization field. This energy deposition from below is superimposed on the release of free energy supplied by the magnetospheric generator. Formulation of this scenario leads to a set of algebraic equations, whose solution provides quantitative answers on the interdependence of current closure, energy deposition, and enhanced auroral energy flux in relation to the imposed tangential electric field. Contrary to earlier expectations, the polarization field appears not as a consequence of current blockage, but as manifestation of its continuation by field-aligned currents and their closure in the magnetosphere. Another consequence of the energy deposition from below is a small modification of the arc's proper motion in the ambient plasma frame. A procedure for evaluating applicable measurements in terms of the underlying physics is given and a concrete example added.
机译：我们对电场的影响切向一个极光弧的基础上分析模型根据极光弧能量的释放磁剪切压力和内部能量有关(Haerendel, 2007)。超过一定的阈值(低),电离层作为电流发生器,或更好变压器、磁层的负载。原因是能源供应的纵我当前的系统类型,所定义的Bostr吗?纬度的II型电流系统弧和主要消耗的极光加速的过程。当前上磁气圈和能量沉积在形式的内部能量和剪切强调,尽管小,是至关重要的这个过程的操作。拖动的磁场和等离子体弧的方向磁性层的高由电极化强度的压力字段。叠加在自由能的释放提供的磁性层的发电机。制定这个场景导致一组代数方程的解决方案提供定量相互依存的答案当前的关闭,能量沉积,增强极光能量通量与实施切向电场。期望,极化字段出现由于目前的堵塞,但是延续的表现field-aligned电流及其闭包的磁气圈。沉积从下面是一个小的修改环境等离子弧的适当的运动框架。测量的物理基础给出一个具体的例子。

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