[1] Using statistical wave power spectral profiles obtained from CRRES and the latitudinal distributions of wave propagation modeled by the HOTRAY code, a quantitative analysis has been performed on the scattering of plasma sheet electrons into the diffuse auroral zone by multiband electrostatic electron cyclotron harmonic (ECH) emissions near L = 6 within the 0000-0600 MLT sector. The results show that ECH wave scattering of plasma sheet electrons varies from near the strong diffusion rate (timescale of an hour or less) during active times with peak wave amplitudes of an order of 1 mV/m to very weak scattering (on the timescale of >1 day) during quiet conditions with typical wave amplitudes of tenths of mV/m. However, for the low-energy (∼100 eV to below 2 keV) electron population mainly associated with the diffuse auroral emission, ECH waves are only responsible for rapid pitch angle diffusion (occasionally near the limit of strong diffusion) for a small portion of the electron population with pitch angles a eq < 20°, dependent on electron energy and geomagnetic activity level. ECH scattering alone cannot account for the rapid loss of plasma sheet electrons during transport from the nightside to the dayside, nor can it explain the formation of the pancake electron distributions strongly peaked at a eq > 70°. Computations of the bounce-averaged coefficients of momentum diffusion and (pitch angle, momentum) mixed diffusion indicate that both mixed diffusion and energy diffusion of plasma sheet electrons due to ECH waves are very small compared to pitch angle diffusion and that ECH waves have little effect on local electron acceleration. Consequently, the multiple harmonic ECH emissions cannot play a dominant role in the occurrence of diffuse auroral precipitation near L = 6, and other wave-particle interaction mechanisms, such as whistler mode chorus-driven resonant scattering, are required to explain the global distribution of diffuse auroral precipitation and the formation of the pancake distribution in the inner magnetosphere.

[1] The evolution of relativistic electron fluxes in the radiation belts is described by the modified Fokker-Plank equation in terms of the radial distance, energy and equatorial pitch angle. In this study we present numerical solutions of the two-dimensional (2-D) and 3-D Fokker-Planck equation including mixed diffusion terms. We use finite differences method with implicit numerical scheme, which is stable for any given time step. We evaluate the importance of the mixed diffusion in 2-D and 3-D cases of the Fokker-Planck diffusion equation for radiation belts simulations. In both cases the mixed diffusion tends to inhibit local acceleration and results in lower relativistic electron fluxes, as compared to the simulation without mixed diffusion. The effect of the mixed diffusion terms is most significant at small pitch angles. The inclusion of mixed diffusion also tends to delay the formation of the peak in phase space density in the recovery phase of a storm. We also perform sensitivity simulation to the assumed wave models, which indicates that an accurate knowledge of the wave parameters is the most important factor.Citation: Subbotin, D., Y. Shprits, and B. Ni (2010), Three-dimensional VERB radiation belt simulations including mixed diffusion,

[1] Radiation belt diffusion codes require, as inputs, precomputed scattering rates, which are currently bounceaveraged in the dipole magnetic field. We present the results of computations of the bounce-averaged quasilinear pitch-angle diffusion coefficients of relativistic electrons for various distances and two MLT in the Tsyganenko 89c magnetic field model. The coefficients were computed for quiet and storm-time conditions. We compare scattering rates bounce-averaged in a non-dipole field model with those in the dipole field. We demonstrate that on the day side the effects of taking into account a realistic magnetic field are negligible at distances less than six Earth radii. On the night side diffusion coefficients may significantly depend on the assumed field model. Pitch-angle scattering rates calculated in the non-dipole field can explain the often observed night-side chorus induced precipitation. The physical explanation for the changes of pitch-angle scattering rates with the field model is presented and discussed. Citation: Orlova, K. G., and Y. Y. Shprits (2010), Dependence of pitch-angle scattering rates and loss timescales on the magnetic field model, Geophys.