A new diffusion matrix for whistler mode chorus waves

Abstract

[1] Global models of the Van Allen radiation belts usually include resonant wave-particle interactions as a diffusion process, but there is a large uncertainty over the diffusion rates. Here we present a new diffusion matrix for whistler mode chorus waves that can be used in such models. Data from seven satellites are used to construct 3536 power spectra for upper and lower band chorus for 1.5 Ä L * Ä 10 MLT, magnetic latitude 0 ı Ä | m | Ä 60 ı and five levels of K p . Five density models are also constructed from the data. Gaussian functions are fitted to the spectra and capture typically 90% of the wave power. The frequency maxima of the power spectra vary with L * and are typically lower than that used previously. Lower band chorus diffusion increases with geomagnetic activity and is largest between 21:00 and 12:00 MLT. Energy diffusion extends to a few megaelectron volts at large pitch angles > 60 ı and at high energies exceeds pitch angle diffusion at the loss cone. Most electron diffusion occurs close to the geomagnetic equator (< 12 ı ). Pitch angle diffusion rates for lower band chorus increase with L * and are significant at L * = 8 even for low levels of geomagnetic activity, while upper band chorus is restricted to mainly L * < 6. The combined drift and bounce averaged diffusion rates for upper and lower band chorus extend from a few kiloelectron volts near the loss cone up to several megaelectron volts at large pitch angles indicating loss at low energies and net acceleration at high energies.

Oblique Whistler-Mode Waves in the Earth’s Inner Magnetosphere: Energy Distribution, Origins, and Role in Radiation Belt Dynamics

“…An alternative approach for the modeling of oblique chorus waves has been used by Horne et al (2013a). They pointed out that the electric field amplitude of oblique whistler- 26 An example of probability distribution P(B 2 w ) derived from Cluster measurements at K p < 2 (black) and K p > 5 (red) (see details of statistics in Artemyev et al 2012c).…”

“…The are several models of wave intensity ∼ B 2 w dependence on geomagnetical activity level (Shprits et al 2007;Meredith et al 2012;Horne et al 2013a;Orlova and Shprits 2014;Glauert et al 2014;). All these models give wave amplitudes differing from each other by some factors ∼ 1-2 depending on the methods of determination of B 2 w as well as the different spacecraft instruments (see a discussion of matching coefficients for different spacecraft measurements in Meredith et al 2012).…”

“…A proper description of electron interactions with chorus wave first requires a good representation of the distribution of wave magnetic power with latitude and geomagnetic activity, which has been provided and progressively updated and improved along the years with the advent of more and more precise and comprehensive satellite measurements (e.g., see Lyons et al 1972;Hayakawa et al 1984;Meredith et al 2001;Li et al 2009;Horne et al 2013a;Meredith et al 2014, and references therein). In many studies, such a distribution of wave power alone has long been thought to be sufficient.…”

Self‐Consistent Modeling of Electron Precipitation and Responses in the Ionosphere: Application to Low‐Altitude Energization During Substorms

“…To incorporate the wave-particle scattering process for electrons, we apply pitch angle diffusion coefficients (D (E)) derived from statistical wave properties (Glauert & Horne, 2005;Glauert et al, 2014;Horne et al, 2013). Two kinds of waves are considered: whistler-mode chorus waves outside the plasmapause and whistler-mode hiss waves inside the plasmapause.…”

Effect of plasma density on diffusion rates due to wave particle interactions with chorus and plasmaspheric hiss: extreme event analysis

“…The wave parameters used in this study are based on values used by Glauert and Horne (2005), revised using values from fits to data from Horne et al (2013). We set f m = 0.3|f ce |,…”