Optimizing Signal Transmission for Controlled Precipitation of Radiation Belt Electrons
Abstract
Coherent whistler mode waves are believed to a play significant role in the dynamics of high energy radiation belt electrons. Specifically, whistler mode waves can lower particle pitch angles and scatter them into the loss cone where they will be lost to the neutral atmosphere. The ability of coherent waves to scatter energetic electrons opens the possibility for controlled precipitation. Controlled precipitation could decrease fluxes of specified electron energies and thus limit damage to satellites that would be otherwise effected by these high energy particles. Additionally, controlled precipitation would be extremely beneficial for scientific studies of the upper atmosphere. Although the impact of injected coherent waves is a well-studied problem in space weather dynamics, understanding exactly what signal transmission format is required for optimizing particle precipitation is still an open area of research.
Determining the signal transmission that results in a desired precipitated flux is a complex problem that requires numerical optimization. We consider precipitation due to short pulses by creating a phase-space grid in the loss cone and tracing particle trajectories backwards until they reach a point where the particle distribution function was unperturbed. The precipitated flux can then be determined by Liouville's theorem, which says that the distribution function is conserved along particle trajectories. Since the particle trajectories depend upon the space-time format of the incident wave, determining the optimal input wave format corresponds to finding the boundary condition that results in a desired precipitated flux. The wave equation is solved using an implicit finite difference scheme such that the entire space-time evolution is determined simultaneously. The particle trajectories are also determined using an implicit scheme such that the entire trajectory is found simultaneously. Using the implicit finite difference formalism, the non-linear optimization problem requires minimizing the difference between the true and desired precipitated flux while solving the wave equation and tracking particle trajectories. This method can be extremely useful to determine the optimum coherent signal transmission format for the desired level of energetic electron precipitation.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMSM33C3600H
- Keywords:
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- 2716 Energetic particles: precipitating;
- MAGNETOSPHERIC PHYSICSDE: 2720 Energetic particles: trapped;
- MAGNETOSPHERIC PHYSICSDE: 2772 Plasma waves and instabilities;
- MAGNETOSPHERIC PHYSICSDE: 2774 Radiation belts;
- MAGNETOSPHERIC PHYSICS