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- Title
Statistical Characteristics of Chorus Second Harmonic Waves in the Earth's Inner Magnetosphere.
- Authors
Deng, Dan; Yuan, Zhigang; Xue, Zuxiang; Huang, Shiyong; Huang, Zheng; Yu, Xiongdong
- Abstract
Recently, lower‐band chorus waves have been determined to cause diffuse auroral precipitation by exciting their second harmonics when the preferred excitation condition is satisfied. In this paper, with observations from the Van Allen Probe mission, we find that chorus second harmonic waves typically occur at L ∼ 4.5–6.5, particularly in the night‐dawn‐noon sector, which is consistent with the distribution of electron diffuse aurora. This observation suggests that chorus second harmonics play a potential role in the generation of diffuse aurora. Additionally, although most second harmonic events of chorus waves are found near the preferred excitation condition under the cold plasma assumption, in our survey, a secondary group is found away from the preferred excitation condition. The deviation is attributed to the significant alteration of the dispersion curve by the contribution from thermal electrons. Our results are helpful for understanding the excitation of chorus second harmonics and their roles in the magnetosphere. Plain Language Summary: The harmonic emissions of electromagnetic waves are often observed in space plasmas. Previous studies indicated that chorus waves with a frequency (f) and a normal angle (θ) satisfying f/fce = (cos θ)/3 are more likely to excite second harmonic waves (fce is the local electron gyrofrequency). However, some second harmonic events that do not satisfy the preferred excitation condition are observed, and their excitation mechanisms have not yet been determined. In this study, we provide statistical evidence for the effects of hot electrons on the generation of the chorus second harmonic beyond the preferred excitation condition predicted under the cold plasma assumption. Based on a survey of burst‐mode data from the Van Allen Probe mission, we obtain these properties of chorus second harmonics, including the amplitude and global spatial distribution. Those properties might be helpful to construct future models of the evolution of magnetospheric particles. Key Points: The global distributions of chorus second harmonic waves are mainly consistent with those of diffuse auroral electron precipitationThe amplitude distribution of chorus second harmonics was obtainedHot electrons lead to deviations of chorus second harmonic generation from the excitation condition under the cold plasma assumption
- Subjects
MAGNETOSPHERE; SECOND harmonic generation; HOT carriers; ELECTRON distribution; THERMAL electrons; ATTOSECOND pulses; HARMONIC maps
- Publication
Journal of Geophysical Research. Space Physics, 2023, Vol 128, Issue 12, p1
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2023JA031995