A Wave Model and Diffusion Coefficients for Plasmaspheric Hiss Parameterized by Plasmapause Location

Abstract

The scattering of electrons via plasmaspheric hiss whistler‐mode plasma waves has profound consequences for the dynamics of electrons in the inner terrestrial magnetosphere, including the radiation belts. Consequently, simulations of inner magnetospheric electron dynamics incorporate hiss wave models, though these models are often parameterized by quantities convenient to describe particle populations (e.g., L shell). However, recent studies have revealed that the spatial distribution of plasmaspheric hiss wave power is only weakly dependent on L shell. Instead, it is dictated by the density structure of the plasmasphere (including radial extent and azimuthal structure). In this work, we create a plasmaspheric hiss wave model, and corresponding particle diffusion coefficients, parameterized by plasmapause location instead of L shell, in order to quantify the importance of including plasmapause organization of hiss waves for inner magnetosphere models. Noticeable differences in electron scattering lifetimes are found when comparing L shell parameterized hiss and plasmapause‐parameterized hiss wave models on the timescales of days for 1 MeV electrons. Comparison of the lifetimes calculated from diffusion around the loss cone also show differences between L shell‐ and plasmapause‐parameterized hiss models. This implies that plasmapause parameterization of hiss waves may be important for modeling specific geomagnetic events.

The Role of Hiss, Chorus, and EMIC Waves in the Modeling of the Dynamics of the Multi‐MeV Radiation Belt Electrons

“…Malaspina et al (2016) emphasized that the hiss wave power can be organized better using the location of the plasmapause in comparison with traditional L‐shell sorting. The model of hiss waves parameterized by the plasmapause location leads to a different scattering rate, and it is under development (Malaspina et al, 2020).…”

Determining the Temporal and Spatial Coherence of Plasmaspheric Hiss Waves in the Magnetosphere

“…Traditionally, empirical models of pitch angle diffusion in the radiation belts have been computed using average magnetospheric parameters, such as number density and magnetic field intensity (e.g., Fok et al., 2011; Glauert et al., 2013; Malaspina et al., 2020; Subbotin & Shprits, 2009). However, recent modeling and data analysis work (Watt et al., 2019, 2021) indicates that the efficacy of diffusion is increased if the variability in hiss wave growth parameters is considered instead of simply using average values.…”

Reconstruction of the Radiation Belts for Solar Cycles 17–24 (1933–2017)

“…Conversely, our results for the 0.5 MeV electrons under produces compared to both the Van Allen Probes and CRRES observations. Given that the simulation results tend to over/underestimate electron fluxes at the lower boundary of the radiation belts for a given energy, a more accurate parameterization of plasmaspheric hiss may be required to produce a more efficient scattering of electrons, especially for the subMeV electrons (Malaspina et al., 2019). There may be potentially missing physical processes.…”