Generation of chorus emissions and acceleration of relativistic electrons associated with magnetic storms

惠斯勒模式合唱波是航天器在地球、木星、土星和天王星的磁层中观测到的电磁辐射，频率在0.05-0.8Ω之间，其中Ω是本地电子回转频率。在地球上，地面上也记录到了合唱发射，在发生磁场扰动时，如磁暴和雷暴，观测到了合唱发射。合唱波包括持续时间短(10-1秒)的离散发射，频率通常随着时间的推移而增加(上升的音调)，当连接到音频放大器时，听起来像黎明时的鸟鸣或蟋蟀的鸣叫声。理论和模拟研究以及观测证据已经证实，在地磁扰动期间，通过回旋共振波-粒子相互作用与和声波相互作用的电子加速是在地球外辐射带产生相对论(&gt；1 MeV)电子的关键机制。经过近40年的合唱波观测和数值研究，直到最近才进行了计算机模拟，成功地模拟了声调上升的合唱发射的产生。我们发现，在合唱产生的模拟中，一些共振电子被相对论转动加速(RTA)和超相对论加速(URA)过程迅速激发。RTA和URA是共振电子被相干哨声模波俘获的特殊形式，构成了在磁化行星辐射带中产生相对论电子的可行机制。计算机模拟表明，由上升音调引起的非线性波增长是合唱波产生的关键因素。

Whistler-mode chorus waves are eletromagnetic emissions that have been observed by spacecraft in the magmetospheres of Earth, Jupiter, Saturn, and Uranus, with frequencies in the range 0.05-0.8 Ω, where Ωis the local electron gyrofrequency. At Earth chorus emissions have also been recorded on the ground Chorus emissions am observed at the time of magnetic field disturbance such as magnetic storms and suhstorms. Chorus waves comprise discrete emissions of short duration (<10-1sec), with frequency typically increasing in time (rising tones), and, when connected to an audio amplifier, sound like bird song at dawn or chirping crickets. Theoretical and modeling studies and observational evidence have established electron acceleration by gyroresonant wave-particle interaction with chorus waves as a key mechanism for generating relativistic (>1 MeV) electrons in the Earth's outer radiation belt during geomagnetically disturbed periods. After nearly four decades of chorus wave observations and numerical studies, only recently have computer simulations been performed that successfully model the generation of chorus emissions with a rising tone. We have found that in the simulation of chorus generation, some resonant electrons are rapidly energized by the processes of relativistic turning acceleration (RTA) and ultra-relativistic acceleration (URA). RTA and URA are particular forms of nonlinear wave trapping of resonant electrons by coherent whistler-mode waves and constitute viable mechanisms for the generation of relativistic electrons in the radiation belts of magnetized planets. The computer simulations reveal that nonlinear wave growth due to the rising tone is the key ingredient in the generation of chorus waves.