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Abstract: Whistler mode waves (100Hz – 30kHz) play a dominant role in the Earth’s dynamic magnetosphere. The magnetosphere is the host of the radiation belts, the regions of trapped high-energy electrons. The interaction of whistler-mode waves with these high-energy electrons is a determining factor of space weather. When it comes to magnetospheric whistler, mode waves there are two main categories: chorus and hiss. Chorus waves are mostly observed outside the plasmapause and the hiss waves are observed inside it. Although there are agreements between the source mechanisms of chorus waves, there is no direct agreement on the source mechanism of hiss waves. Some of the proposed source mechanisms for hiss waves are chorus waves and lightning-generated non-ducted whistler waves.

In our recent work, we performed a comprehensive numerical raytracing study of whistler-mode wave power to investigate wave power distribution in relation to the plasmapause. We considered a finite electron and ion temperature of 1eV for the ambient plasma to simulate the realistic magnetosphere. Both Landau damping and wave growth were also taken into account using isotropic and bi-Maxwellian hot electron distributions. Three primary equatorial source locations at L=2, Lpp, and L=5, corresponding to within the plasmasphere, at the plasmapause, and outside the plasmapause, are investigated for MLT values of 00, 06, 12, and 18. At each location, waves are launched with a range of initial wave normal angles (−70° to 20°).

The simulated wave power distributions are compared with observations from the EMFISIS instrument on Van Allen Probe A. Correspondence between the simulated distribution and the observations requires a weighting of the source regions. Results suggest that the majority of whistler-mode power in the plasmasphere is sourced from within the plasmasphere itself and near the plasmapause. Only at noon (MLT 12) is wave power sourced primarily from at and outside the plasmapause.

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Meeting ID: 927 5142 0885
Passcode: Plasma