空间科学学报2025，Vol.45Issue(5)：1188-1196,9.DOI:10.11728/cjss2025.05.2024-0187
合声波引起的外辐射带相对论电子投掷角分布快速演化
Rapid Evolution of the Relativistic Electron Pitch Angle Distributions Caused by Chorus in the Earth's Outer Radiation Belt
摘要
Abstract
The pitch angle,defined as the angle between a charged particle's velocity vector and the ambient magnetic field,is a key parameter that governs the particle's motion within the magnetic field.In Earth's outer radiation belt,energetic electrons display diverse Pitch Angle Distribution(PAD)pat-terns.These patterns are influenced by various factors and frequently undergo changes,typically occur-ring over timescales ranging from several hours to several days.Investigating electron PAD variations and uncovering the underlying physical mechanisms are of significant importance for understanding the dynamic evolution of the Earth's outer radiation belt.This paper utilizes Van Allen Probe-B data to conduct a detailed analysis of the evolution of relativistic electron PADs in the outer radiation belt dur-ing an event that occurred from 15:19 UT to 15:49 UT on 7 September 2016.During this period,the satellite was operating near its apogee,with a slow orbital speed and minimal changes in spatial position,remaining approximately at the location L≈5.8,MLT≈2 and Mlat≈1.7°.As a result,the impact of po-sitional changes on the observational results can be considered negligible.Satellite observations revealed that relativistic(Ek≥1 MeV)electron PADs transitioned from butterfly patterns to flat-top patterns during this period,within a timescale of only 30 minutes,which is significantly shorter than previously reported cases.Concurrently,intense whistler-mode chorus waves were detected in this region.Based on observational data,we calculated the chorus-driven diffusion coefficients of relativistic electrons.We then simulated the evolution of electron PADs by solving a Fokker-Planck equation.The simulation results indicate that the diffusion driven by whistler-mode chorus waves is the primary physical mechanism re-sponsible for the transformation of the electron PADs during this event.The research presented in this paper further demonstrates the significant role of chorus waves in the evolution of the radiation belts.关键词
地球辐射带/相对论电子/哨声模合声波/波粒相互作用/投掷角分布Key words
Earth's radiation belts/Relativistic electrons/Whistler-mode chorus waves/Wave-particle interactions/Pitch angle distributions分类
地球科学引用本文复制引用
岳佳旭,赵晖,杨昶,张赛..合声波引起的外辐射带相对论电子投掷角分布快速演化[J].空间科学学报,2025,45(5):1188-1196,9.基金项目
国家自然科学基金项目(42374215)和湖南省教育厅资助科研项目(21A0212)共同资助 （42374215）
