Quasi‐adiabaticity in bifurcated current sheets
Quasi‐adiabaticity in bifurcated current sheets
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DOI：
10.1029/2005gl025463
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发表时间：
2006-03
影响因子：
5.2
通讯作者：
D. Delcourt;H. Malova;L. Zelenyi
中科院分区：
文献类型：
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作者：
D. Delcourt;H. Malova;L. Zelenyi
我们研究了“分叉”（双峰）电流片中带电粒子的非线性动力学。当绝热性参数κ为1阶时，粒子的磁矩变化可以忽略不计。这种行为与在这种κ值下在单峰电流片中实现的突出磁矩散射形成对比。它类似于准绝热（Speiser型）行为，这是由于中平面附近的快速振荡和该平面附近的缓慢陀螺运动之间的共振而在κ ε 1处获得的。我们证明了κ <$1粒子束可以在分叉电流片的下游形成，它沿着磁力线传播到高纬度。因此，准绝热性和相关的束形成发生在双峰电流片中比单峰电流片中的κ值大得多的情况下，或者等效地发生在较低的粒子能量和/或较弱的场反转的情况下。
We examine the non‐linear dynamics of charged particles in “bifurcated” (double‐humped) current sheets. We show that, when the adiabaticity parameter κ is of the order unity, particles experience a negligible change of magnetic moment. Such a behavior contrasts with the prominent magnetic moment scattering that is achieved in single‐humped current sheets at such κ values. It resembles the quasi‐adiabatic (Speiser‐type) behaviors that is obtained at κ ≪ 1 as a result of resonance between the fast oscillation about the midplane and the slow gyromotion near this plane. We demonstrate that beams of κ ≈ 1 particles may form downstream of bifurcated current sheets, which propagate along the magnetic field lines up to high latitudes. Quasi‐adiabaticity and associated beam formation thus occur at significantly larger κ values in double‐humped current sheets than in single‐humped ones, or equivalently for lower particle energy and/or weaker field reversal.