Cross-scale coupling in the auroral acceleration region
Cross-scale coupling in the auroral acceleration region
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DOI：
10.1029/2011gl049185
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发表时间：
2011-10-18
影响因子：
5.2
通讯作者：
Carlson, C. W.
中科院分区：
文献类型：
--
作者：
Chaston, C. C.;Seki, K.;Carlson, C. W.
极光光度区域内的高分辨率成像揭示了复杂的、高度结构化的、动态的、通常是漩涡的形式，这些形式在几秒钟或更短的时间尺度上演化。这些特征本质上是多尺度的，具有不同的大小，以不同的速度移动和演变。最近的分析表明，这些运动的尺度依赖性如何能够为通过极光加速区的当前冰盖中跨尺度的能量传输的性质提供新的见解。然而，推动这种传输并因此促进粒子加速和形成明亮而充满活力的极光的过程仍然未知。这不仅是促进对极光弧形成的理解的一个基本问题，而且对于理解电流片中的耗散和粒子加速也是一个基本问题。在这篇前沿文章中，我们展示了专门的星载极光图像如何与磁性共轭场和粒子测量相结合，来促进对这一宇宙物理过程的理解。通过将这些测量与数值模拟相结合，我们展示了流动剪切、磁场重联和撕裂如何向更小的尺度发起级联，并共同形成、塑造和构造极光形式。模拟表明，这些过程朝着结构磁场(B(X))和垂直于地磁场的波数(k(Y))的强健标度演化，其中B(X)(2)(k(Y))/Delta k(Y)类似于k(Y)(-7/3)。引文：Chaston，C.C.，K.Seki，T.Sakanoi，K.Asamura，M.Hirahara，C.W.Carlson(2011)，《极光加速区的跨尺度耦合》，地球物理。莱特，38，L20101，DOI：10.1029/2011GL049185。
High resolution imaging within regions of auroral luminosity reveal complex, highly structured dynamic and often vortical forms which evolve on time scales of the order of several seconds and less. These features are inherently multi-scale in nature with different sizes moving and evolving at different rates. Recent analyses have shown how the scale dependency of these motions can provide new insights into the nature of energy transport across scales occurring in current sheets through the auroral acceleration region. However the processes driving this transport and thus facilitating particle acceleration and the formation of bright and dynamic aurora remain unknown. This is a basic issue not only for advancing understanding of auroral arc formation but moreover for understanding dissipation and particle acceleration in current sheets generally. In this Frontier article we show how dedicated space-borne auroral imagery combined with magnetically conjugate field and particle measurements can be used to advance understanding of this universal physical process. By coupling these measurements with numerical simulations we show how flow shear, magnetic reconnection and tearing may launch a cascade toward smaller scales and conspire to form, shape and structure auroral forms. The simulations show that these processes evolve toward a robust scaling of structured magnetic fields (B(x)) with wavenumber (k(y)) perpendicular to the geomagnetic field where B(x)(2)(k(y))/Delta k(y) similar to k(y)(-7/3) as observed. Citation: Chaston, C. C., K. Seki, T. Sakanoi, K. Asamura, M. Hirahara, and C. W. Carlson (2011), Cross-scale coupling in the auroral acceleration region, Geophys. Res. Lett., 38, L20101, doi:10.1029/2011GL049185.