“…Radial and energy diffusion are ignorable because the frequency of the EMIC waves is well above the drift frequency and well below the gyrofrequency of the resonant particles [ Kennel , 1966]. The bounce-averaged diffusion equation for pure pitch angle scattering can be written as [ Davidson and Walt , 1977; Lyons , 1973; Lyons and Williams , 1984; Shao et al , 2009]
where T ( α 0 )=1.3802−0.3198(sin( α 0 )+ sin1/2( α 0 )) is the normalized bounce time, f 0 is the trapped electron phase space density, α 0 is the equatorial pitch angle, 〈 D α α ( α 0 , E )〉 is the bounce-averaged pitch angle diffusion coefficient, and τ atm is the timescale for losses to the atmosphere. Assuming that losses occur only from within the loss cone and that the loss cone is emptied twice per bounce period, we take τ atm to be half of the bounce period inside the loss cone and infinite outside the loss cone [ Lyons , 1973; Davidson and Walt , 1977; Lyons and Williams , 1984; Shao et al , 2009].…”