Academic Journal
Generation of Falling‐Tone Whistler‐Mode Chorus Waves in the Earth's Magnetosphere.
| Τίτλος: | Generation of Falling‐Tone Whistler‐Mode Chorus Waves in the Earth's Magnetosphere. |
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| Συγγραφείς: | Chen, Huayue1 (AUTHOR) huayue_chen@foxmail.com, Wang, Xueyi2,3 (AUTHOR) wangxueyi2023@gmail.com, Chen, Rui3 (AUTHOR), Omura, Yoshiharu4 (AUTHOR), Chen, Lunjin1 (AUTHOR), Zhao, Hong3 (AUTHOR), Hsieh, Yi‐Kai4 (AUTHOR) |
| Πηγή: | Geophysical Research Letters. 8/16/2026, Vol. 53 Issue 15, p1-11. 11p. |
| Θεματικοί όροι: | *Magnetosphere, *Electromagnetic waves, *Radiation belts, *Space plasmas, *Magnetic dipoles |
| Περίληψη: | Chorus waves are intense whistler‐mode emissions in space that play a key role in regulating energetic electron dynamics in the hazardous radiation belt. While rising‐tone chorus has been extensively studied, the generation mechanism of falling‐tone chorus remains a long‐standing problem. Using Van Allen Probe A observations, we reveal that falling‐tone chorus in Earth's magnetosphere originates on the downstream side of the magnetic equator along the wave propagation direction, in contrast to the upstream source of rising‐tone chorus. Guided by the typical magnetospheric plasma parameters, we perform the first simulation of falling‐tone chorus in a dipole magnetic field representative of Earth's magnetosphere and reproduce its downstream source region. We further demonstrate that falling‐tone chorus is excited through nonlinear interactions with resonant electrons, where both wave growth and frequency chirping are triggered by resonant currents. Our study fills a critical gap in understanding the nonlinear generation of chorus waves under realistic magnetospheric conditions. Plain Language Summary: Whistler‐mode chorus waves are intense electromagnetic emissions widely observed in space and play a significant role in both the formation and depletion of the hazardous radiation belt. A characteristic feature of chorus is its rapid frequency chirping, yet the underlying physical mechanism remains incompletely understood. This is partly because falling‐tone chorus, characterized by a decreasing frequency over time, has been less entensively investigated. Using observations from Van Allen Probe A, we find that while both types of chorus are generated near the magnetic equator, falling‐tone chorus originates on the downstream side along the wave propagation direction, in contrast to the upstream source of rising‐tone chorus. Guided by realistic plasma parameters in observations, we perform a simulation that successfully reproduces falling‐tone chorus in the downstream region. The source region is controlled by the balance between the frequency chirping and the background magnetic field gradient, and the wave excitation is determined by nonlinear wave‐particle interactions. This work provides the first simulation of falling‐tone chorus in a dipole magnetic field and fills a critical gap in understanding its nonlinear generation. Key Points: Observational data reveal that falling‐tone chorus originates downstream of the magnetic equator while rising‐tone chorus arises upstreamWe present the first simulation of falling‐tone chorus in a dipole magnetic field, with waves self‐consistently excited by energetic electronsThe simulation shows that falling‐tone chirping is associated with positive resonant currents aligned with the wave magnetic field perturbation [ABSTRACT FROM AUTHOR] |
| Βάση Δεδομένων: | Academic Search Index |
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