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Statistical Properties and Distributions of Whistler-Mode Waves in Jupiter’s Magnetosphere

Presentation #309.08 in the session Giant Planet Magnetospheres, Ionospheres and Aurorae (Oral Presentation)

Published onOct 23, 2023
Statistical Properties and Distributions of Whistler-Mode Waves in Jupiter’s Magnetosphere

We investigate the statistical distributions of whistler-mode wave frequency spectrum using Juno Waves measurements in Jupiter’s inner and middle magnetosphere. Whistler-mode chorus and hiss waves are commonly observed across a wide range of magnetic latitudes at M < 20, and could cause pitch angle scattering and acceleration of energetic electrons at energies above 1 keV. Using the wave electric to magnetic power ratio, we categorize the whistler-mode waves into quasi-parallel and oblique components. Our survey indicates that the chorus wave power closely correlates the variation of electron gyrofrequency (fce), predominantly occupying the 0.05 - 1 fce range for different M shells. Conversely, the hiss wave power remains stable at frequencies below 1 kHz. The chorus and hiss wave powers merge at high M shells or at high magnetic latitudes, suggesting that the hiss waves originate from the chorus waves generated at high M shells. The inner edge of the Io plasma torus acts as a cutoff point for both chorus and hiss waves, exhibiting little wave power at M < 5.5. This is due to the inefficiency of chorus wave generation in the extremely low-density region and the reflection of hiss waves by the density gradient. The wave electric to magnetic power ratio increases with increasing latitude, suggesting that the waves are mostly quasi-parallel at equator and become more oblique at higher latitudes. This observation supports the scenario that the whistler-mode waves are generated by anisotropic electron distributions at the equator and propagate to higher latitudes with increasing wave normal angles. Our study provides evidences for the various sources of whistler-mode waves in Jupiter’s magnetosphere, and statistical wave frequency spectra which can be incorporated in future radiation belt models.

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