NWC人工甚低频台站信号产生“条缕状”准捕获电子能谱的模拟研究  

Simulation study on“Wisp”electron spectra generated by NWC very low frequency transmitter signals

作　　者：刘阳希子 项正 周晨[1] 倪彬彬[1] 董俊虎 胡景乐 王建行 郭浩智 Liu Yang-Xi-Zi;Xiang Zheng;Zhou Chen;Ni Bin-Bin;Dong Jun-Hu;Hu Jing-Le;Wang Jian-Hang;Guo Hao-Zhi(School of Electronic Information,Wuhan University,Wuhan 430072,China)

机构地区：[1]武汉大学电子信息学院,武汉430072

出　　处：《物理学报》2024年第20期286-299,共14页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:42025404,42188101,42174190);国家重点研发计划(批准号:2022YFF0503700);中国科学院战略性先导科技计划(B类)(批准号:XDB41000000)资助的课题.

摘　　要：遍布全球的人工甚低频台站发射的信号主要用于对潜通信,在夜间,这些信号可以泄漏进磁层与内辐射带中几十至几百keV电子发生回旋共振,从而导致电子沉降.这一过程是导致内辐射带电子损失的重要原因,也是磁层-电离层耦合过程中能量和物质输运的重要环节.被台站信号散射的电子呈现出能量随L增加而减小的“条缕状”能谱结构,与台站信号和电子的一阶回旋共振能量曲线相符.低轨卫星可以对“条缕状”能谱结构进行清晰地观测,为研究近地空间波粒相互作用提供了重要契机.本文基于Drift-Diffusion-Source模型,复现了DEMETER卫星于2009年3月19日多个轨道测量的NWC台站信号导致的“条缕状”能谱,量化了NWC台站信号对辐射带电子的散射作用,明晰了NWC台站信号的幅度和传播角,揭示了内辐射带电子漂移过程中的动态变化规律,为开发人工影响辐射带技术提供了重要理论参考.Very low frequency(VLF)signals emitted by worldwide spread ground-based man-made transmitters mainly propagate in Earth-ionospheric waveguides and are used for submarine communication.A portion of these signals penetrate the ionosphere and leak into the magnetosphere when the ionospheric electron density decreases on the nightside due to the attenuated sunlight.The VLF transmitter signals in the magnetosphere can scatter electrons with energy of several hundred keV in the inner radiation belt into the drift loss cone through cyclotron resonance.This is an important loss mechanism for electrons in the inner radiation belt and plays an important role in transferring energy and mass from magnetosphere to ionosphere.Electrons scattered by transmitter signals exhibit a“wisp”characteristic in L-Ek spectrum,satisfying the first-order cyclotron resonance relationship between the electrons and the transmitter signals.The“wisp”spectrum can be clearly observed by low earth orbit satellites,presenting opportunities to study wave-particle interactions in near-Earth space.In this study,using the Drift-Diffusion-Source model,we reproduce the“wisp”spectrum formed by scattering effects of NWC transmitter signals observed by DEMETER satellite on March 19,2009.Our simulation results suggest that the equatorial pitch angle of electrons,observed by DEMETER,varies with the longitude,resulting in distinctions in the observed“wisp”spectrum along different longitudes.Specifically,as the satellite approaches South Atlantic Anomaly(SAA)region,both the energy range and flux level of the observed“wisp”spectrum gradually increase.When the previously studied wave normal angle model(with a central wave normal angle of 60°)and the background electron density model are used,the energy range of the simulated“wisp”spectra is higher than the observed value.Adjusting the central wave normal angle to 40°or increasing the background density by a factor of 1.3,the simulated results accord well with the observations.Our results

关 键 词：地球辐射带 波粒相互作用 人工甚低频台站信号 电子投掷角扩散 

分 类 号：V443[航空宇航科学与技术—飞行器设计]