Effect of Kinetic Alfvén Waves on Electron Transport in an Ion-Scale Flux Rope

At the Earth's magnetopause, the electron transport due to kinetic Alfvén waves(KAWs) is investigated in an ion-scale flux rope by the Magnetospheric Multiscale mission. Clear electron dropout around 90° pitch angle is observed throughout the flux rope, where intense KAWs are identified. The KAWs can effectively trap electrons by the wave parallel electric field and the magnetic mirror force, allowing electrons to undergo Landau resonance and be transported into more field-aligned directions. The pitch angle range for the trapped electrons is estimated from the wave analysis, which is in good agreement with direct pitch angle measurements of the electron distributions. The newly formed beam-like electron distribution is unstable and excites whistler waves,as revealed in the observations. We suggest that KAWs could be responsible for the plasma depletion inside a flux rope by this transport process, and thus be responsible for the formation of a typical flux rope.     

动摩擦作用下非光滑振动系统的黏滑颤振分析

研究了一类含Dankowicz动摩擦的非光滑振动系统的动力学行为。建立了含Dankowicz动摩擦和弹性接触的非光滑振动系统的力学模型,分析了系统的运动过程。利用数值仿真方法探讨了系统运动在滑移-黏滞-碰撞接触-颤振之间转换的动力学行为。结果表明,在一定系统参数下,系统存在多种黏滑和颤振之间转换的运动形式,如周期滑移-黏滞-碰撞、周期滑移-黏滞-颤振-碰撞等。