摘要
超光速(相速度大于光速)电磁波是广泛存在于空间等离子中的高频电磁波,总结了超光速电磁波的产生机制——回旋微波激射不稳定性,介绍了超光速波在地球磁层中的传播特性,分析了其从高纬极光源区传播到低纬区域的基本原因:磁暴时由于等离子层顶压缩,超光速波传播时不会遇上反射,从而能向下传播。重点介绍了超光速波产生的地球辐射带区域高能电子的随机加速与投掷角扩散过程。发现超光速波能量扩散过程一般大于投掷角扩散过程,在合适的条件下超光速波对高投掷角的高能电子主要起随机加速作用,而对低投掷角的高能电子主要起投掷角扩散作用。这些最新进展有助于进一步了解超光速电磁波的激发与传播特性,以及地球辐射带高能电子的动力学行为。
Superluminous（the phase speed higher than the speed of light） electromagnetic waves are widely present in the space plasma with high frequencies.Here,we briefly introduce their generation mechanism—Cyclotron Maser Instability（CMI）.We present discussion on the propagating characteristics of superluminous waves in the Earth′s magnetosphere.During high geomagnetic activity,since the plasmapause position moves inward closer to the Earth,the superluminous waves can propagate from their source cavity downward and even through the equatorial plane due to no reflection.We focus on pitch angle scattering and stochastic acceleration of energetic electrons induced by superluminous waves in the radiation belts.Current works show that energy diffusion resulting from such waves is generally higher than pitch angle scattering.Under appropriate conditions,superluminous waves may contribute to both the stochastic acceleration of electrons with larger pitch angle and the loss process of electrons with smaller pitch angles.These recent progresses provide further understanding of the instability and propagation of superluminous waves,as well as the dynamics of highly energetic electrons in the Earth′s radiation belts.
出处
《地球科学进展》
CAS
CSCD
北大核心
2011年第5期493-498,共6页
Advances in Earth Science
基金
国家自然科学基金项目"超光速电磁波对高能电子随机加速和投掷扩散的研究"(编号:40774078)资助
关键词
超光速电磁波
传播特性
随机加速
投掷角扩散
Superluminous electromagnetic waves
Propagating characteristic
Stochastic acceleration
Pitch angle scattering.
