Prompt Appearance of Large‐Amplitude EMIC Waves Induced by Solar Wind Dynamic Pressure Enhancement and the Subsequent Relativistic Electron Precipitation

• Published in: Journal of geophysical research. Space physics 2023-07, Vol.128 (7), p.n/a
• Main Authors: Yan, Yun, Yue, Chao, Ma, Qianli, Zhou, Xu‐Zhi, Zong, Qiu‐Gang, Fu, Haobo, Xie, Zi‐Kang, Yin, Ze‐Fan, Li, Yu‐Xuan
• Format: Article
• Language: English
• Subjects: Amplitudes; Cyclotrons; Dynamic pressure; electromagnetic ion cyclotron (EMIC) waves; Electron precipitation; Electrons; Fluxes; inner magnetosphere; Jupiter; Longitudinal waves; Magnetopause; Pitch (inclination); Plasma density; Plasma waves; POES satellites; Polarization; Proton precipitation; radiation belt; Relativistic effects; relativistic electron precipitation; Satellite observation; Satellites; Saturn; Scattering; Signatures; Solar wind; solar wind dynamic pressure enhancement; Solar wind structure; Space density; Wave generation; wave‐particle interaction
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2023JA031399

Electromagnetic ion cyclotron (EMIC) waves play an important role in relativistic electron dynamics. In this study, we find a large‐amplitude EMIC wave event induced by the prompt enhancement of solar wind dynamic pressure on 6 November 2015. These large‐amplitude EMIC waves are simultaneously observed by multiple satellites over 13 hr in magnetic local time (MLT) with a peak amplitude of ∼4 nT. Satellites at different locations observed different bands of EMIC waves, implying the importance of background plasma density in EMIC wave generation. Electron pitch angle distributions show obvious responses to EMIC wave activities. During EMIC wave appearance, the fluxes of relativistic electrons with pitch angles around 90° increase, while the fluxes of field‐aligned relativistic electrons decrease, showing distinct “bite‐out” signatures, indicating pitch angle scattering by EMIC waves, and the scattering efficiency depends on the amplitude and polarization of EMIC waves. Combined with phase space density profiles of electrons that are nearly constant at energies below the minimum resonant energy of electrons (Emin) but show dropout at energies above the Emin after EMIC wave activities, we conclude that large‐amplitude EMIC waves can cause rapid electron loss down to several hundred keV. In addition, simultaneous observations of hundreds of keV electron precipitation and tens of keV proton precipitation by Polar Operational Environmental Satellites near the region where EMIC waves are observed, provide direct evidence of relativistic electron precipitation caused by the large‐amplitude EMIC waves, ultimately driven by solar wind structures. Plain Language Summary Solar wind dynamic pressure enhancement leads to the compression of the magnetopause, which could induce various plasma waves. Our study shows the prompt appearance of large‐amplitude EMIC waves after the impact of solar wind dynamic pressure enhancement. The excited EMIC waves are observed simultaneously by multiple satellites over 13 hr in magnetic local time. Different bands of EMIC waves are observed by satellites at different locations, which may be related to the background plasma density. During EMIC wave appearance, the fluxes of relativistic electrons with pitch angles around 90° increase, while the fluxes of field‐aligned relativistic electrons decrease, showing distinct “bite‐out” signatures, and the scattering efficiency depends on the amplitude and polarization of EMIC waves. Besides, phas