Interaction of ring current and radiation belt protons with ducted plasmaspheric hiss: 1. Diffusion coefficients and timescales

Protons that are converted into the inner magnetosphere in response to enhanced magnetic activity can resonate with ducted plasmaspheric hiss in the outer plasmasphere via an anomalous Doppler‐shifted cyclotron resonance. Plasmaspheric hiss is a right‐hand‐polarized electromagnetic emission that is observed to fill the plasmasphere on a routine basis. When plasmaspheric hiss is confined within field‐aligned ducts or guided along density gradients, wave normal angles remain largely below 45°. This allows resonant interactions with ions at typical ring current and radiation belt energies to take place. Such field‐aligned ducts have been observed both within the plasmasphere (Kozyra et al., 1987 a ; Koons, 1989) and in regions outside of the plasmasphere (Chan and Holzer, 1976). Wave intensities are estimated using statistical information from studies of detached plasma regions (Chan et al., 1974). Diffusion coefficients are presented for a range of L shells and proton energies for a fixed wave distribution. Harmonic resonances in the range n = ±100 are considered in order to include interactions between hiss at 100 Hz to 2 kHz frequencies, and protons in the energy range between ∼10 keV and 1000 keV. Diffusion timescales are estimated to be of the order or tens of days and comparable to or shorter than lifetimes for Coulomb decay and charge exchange losses over most of the energy and spatial ranges of interest.