We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Study on Source Region and Generation Mechanism of Oblique Whistler‐Mode Waves in the Earth's Magnetosphere.
- Authors
Gao, Xinliang; Lu, Quanming; Kang, Ning; Ke, Yangguang; Ma, Jiuqi; Tsurutani, Bruce; Chen, Rui; Chen, Huayue
- Abstract
Oblique whistler‐mode waves are as important as quasi‐parallel waves in regulating electron dynamics in radiation belts. However, their generation mechanism and corresponding source region are still under debate. By analyzing nearly 7‐year Van Allen Probe‐A data, we have thoroughly investigated lower‐band (<0.5fce ${f}_{\mathrm{c}\mathrm{e}}$) and upper‐band (>0.5fce ${f}_{\mathrm{c}\mathrm{e}}$) oblique whistler‐mode waves in the Earth's inner magnetosphere. We found the majority of poleward propagating oblique waves preferentially occur at relatively larger magnetic latitudes (MLATs), and their favored MLATs are strongly dependent on magnetic local time. Combined with ray tracing simulation results, it is proposed that parallel waves generated at the equator propagate toward poles and turn oblique to the ambient magnetic field, leading to oblique waves detected at large |MLAT|. This propagation effect is the main cause of oblique whistler‐mode waves in the Earth's magnetosphere. There also exist some equatorward propagating oblique waves, which are mainly confined within ±5° $\pm 5{}^{\circ}$ around midnight and considered to be locally excited. Our study provides a comprehensive understanding of the generation and distribution of oblique whistler‐mode waves in the Earth's magnetosphere. Plain Language Summary: Quai‐parallel whistler‐mode waves have attracted more attention than oblique whistler‐mode waves in the community, since oblique waves typically have the smaller magnetic amplitude in the Earth's magnetosphere. However, based on Cluster data, Artemyev, Agapitov, et al. (2015), https://doi.org/10.1038/ncomms8143 suggested that oblique whistler‐mode waves may carry up even more wave energy involved in wave‐particle resonant interactions. Therefore, we have thoroughly studied those oblique waves by analyzing 7‐year Van Allen Probe‐A wave spectrum data, especially focusing on the source region and physical causes. Actually, there already exist two principal candidates in the literature: propagation effects and local generation. Our statistical results show that most of oblique whistler‐mode waves are poleward propagating, which preferentially occur at relatively larger latitudes and show strong dependence on magnetic local time. Our ray tracing results are consistent with observations, suggesting the propagation effect is the dominant generation mechanism in the Earth's magnetosphere. We also find some local excitation effects, but only for equatorward propagating oblique waves near the equator in the midnight sector. Key Points: Using 7‐year Van Allen Probe‐A data, we have statistically studied oblique whistler‐mode waves in the Earth's magnetosphereMost of oblique waves are poleward propagating and their favored magnetic latitudes increase with magnetic local time, supporting propagation effect as the main causeThere also exist some equatorward propagating oblique waves confined within 5 $5$° in the midnight sector, which may be locally excited
- Subjects
MAGNETOSPHERE; RAY tracing; RADIATION belts; WAVE energy; COMMUNITIES
- Publication
Journal of Geophysical Research. Space Physics, 2022, Vol 127, Issue 9, p1
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2022JA030804