Estimating quasi-linear diffusion coefficients for varying values of density ratio

Document Type

Article

Publication Date

1-1-2024

Abstract

This paper considers a method for estimating bounce-averaged quasi-linear diffusion coefficients due to whistler-mode waves for a specified ratio of plasma frequency to gyrofrequency, (Formula presented.), using values precomputed for a different value of that ratio. This approach was recently introduced to facilitate calculations associated with the “POES technique,” generalized to infer both wave intensity and cold plasma density from measurements of particle fluxes near the loss cone. The original derivation was justified on the basis of parallel-propagating waves but applied to calculations with much more general models of the waves. Here, we justify the estimates, which are based on equating resonant frequencies for differing values of (Formula presented.) and energy, for wide ranges of wave normal angle, resonance number, energy, and equatorial pitch angle. Refinements of the original estimates are obtained and tested numerically against full calculations of the diffusion coefficients for representative wave models. The estimated diffusion coefficients can be calculated rapidly and generally give useful estimates for energies in the 30-keV–300-keV range, especially when both relevant values of the ratio (Formula presented.) are large.

Identifier

85212672169 (Scopus)

Publication Title

Frontiers in Astronomy and Space Sciences

External Full Text Location

https://doi.org/10.3389/fspas.2024.1470742

e-ISSN

2296987X

Volume

11

Grant

2021RVCOR002

Fund Ref

Air Force Research Laboratory

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