Modeling of magnetospheric chorus waves with 2D TRISTAN-MP PIC code
Abstract
Magnetospheric chorus waves are one of the most intense wave phenomena in the Earth's inner magnetosphere, and they play important role in particle dynamics in the outer radiation belt. These waves are observed as series of quasi-coherent wave-packets with rising or, sometimes, falling frequency. Chorus waves are generated in the equatorial region as a result of whistler instability of the anisotropic electron distribution. Their frequency chirping is generally assumed to be a non-linear phenomenon associated with formation of a non-linear current and corresponding electromagnetic holes or hills. Due to non-linear nature of these waves, the opportunities of their theoretical study are rather limited, and self-consistent numerical simulations are required.
We present the results of simulation of whistler instability and chorus generation with the 2D full Particle-in-Cell code TRISTAN-MP. This code models self-consistent dynamics of three particle populations: ions, cold electrons with isotropic Maxwellian distribution, and hot electrons initially having anisotropic relativistic Maxwell-Juttner distribution. We successfully generated chorus waves using TRISTAN-MP code. We investigated the dependence of chorus generation process on the distribution anisotropy and background magnetic field inhomogeneity. Our results are consistent with the one-dimensional simulations and theory, which allow only parallel waves to be considered. According to the theory, there exists a wave amplitude threshold below which no non-linear particle trapping takes place, hence, the chorus waves are not generated. Higher inhomogeneity leads to higher threshold amplitude, thus, it suppresses the generation of chorus waves. These properties of the chorus wave generation are reproduced in our 2D simulations. We hope our results will be useful for future modeling and better theoretical understanding of magnetospheric chorus waves. The work was supported by NSF grant 1502923 and NASA Van Allen Probes RBSPICE instrument project by JHU/APL Subcontract No. 937836270. Computational facilities were NCAR UCAR cluster in Cheyenne, WY, USA, and NJIT Kong cluster at New Jersey Institute of Technology, Newark, NJ, USA.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMSM43D3608K
- Keywords:
-
- 2716 Energetic particles: precipitating;
- MAGNETOSPHERIC PHYSICSDE: 2720 Energetic particles: trapped;
- MAGNETOSPHERIC PHYSICSDE: 2774 Radiation belts;
- MAGNETOSPHERIC PHYSICSDE: 7867 Wave/particle interactions;
- SPACE PLASMA PHYSICS