A theoretical investigation of banded chorus
- 1 April 1974
- journal article
- research article
- Published by Cambridge University Press (CUP) in Journal of Plasma Physics
- Vol. 11 (2) , 189-212
- https://doi.org/10.1017/s0022377800024600
Abstract
This paper is a computational study of nonlinear resonant particle trajectories in wave fields consisting of an array of narrow-band waves of closely spaced frequencies and wavenumbers. It looks at two analogous systems, cyclotron resonance with a whistler wavefield and Landau resonance with an electrostatic wave field. It is found that the wave array is able to trap particles in much the same way as a single mode. Inhomogeneity plays a vital role by causing the energy of trapped particles to change. The nonlinear resonant particle current is such as to preserve the modal structure of the wave field, and it does not change the frequency of an individual mode. Power distribution amongst the modes is far from even. Most of the energy goes into the mode at one end of the array, depending on the direction of the inhomogeneity. Also, nonlinear resonant particle excitation of a broad band signal was found to cause spectral structuring to develop automatically. The theory was applied to one of Coroniti's FTRS analyses of banded chorus elements. The observed spectral behaviour closely accorded with the computational results. The numbers involved fitted the theory very well, and strongly suggested that nonlinear cyclotron resonant particle excitation is the mechanism for banded chorus.Keywords
This publication has 7 references indexed in Scilit:
- The sideband instability of electrostatic waves in an inhomogeneous mediumPlanetary and Space Science, 1973
- Nonlinear Evolution of Whistler InstabilitiesPhysics of Fluids, 1972
- STOCHASTIC INSTABILITY OF NON-LINEAR OSCILLATIONSSoviet Physics Uspekhi, 1972
- Theory of triggered VLF emissionsJournal of Geophysical Research, 1971
- Fast time resolved spectral analysis of VLF banded emissionsJournal of Geophysical Research, 1971
- Banded chorus-A new type of VLF radiation observed in the magnetosphere by OGO 1 and OGO 3Journal of Geophysical Research, 1969
- A theory of discrete VLF emissions from the magnetosphereJournal of Geophysical Research, 1967