Wave-particle interaction plays an important role for radiation belt electron diffusion in the
momentum space. Several different types of waves can contribute to the electron diffusion [1].
Here we focus on the lower-hybrid waves (the so-called ‘equatorial noise’), which are
frequently observed near the geomagnetic equator [2, 3]. The lower hybrid waves are in the
frequency range between the proton gyrofrequency and the lower-hybrid frequency, and are
propagating nearly perpendicular to the background magnetic field with almost linear
polarization.
In this presentation, we discuss the pitch-angle and energy diffusion of electrons caused by
the lower-hybrid waves, performing one-dimensional test particle simulations. We specify the
lower-hybrid waves based on the cold plasma dispersion relation and assume a Gaussian
spectrum of the waves, in uniform and straight background magnetic fields. An important
physical parameter is the wave propagation angle relative to the background magnetic fields.
This angle is varied from 80 to 90 degrees. We evaluate the energy and the pitch-angle
diffusion coefficients by taking an ensemble average of the test particle electrons. We will
also discuss evolution of the electron distributions as functions of the pitch-angle and energy.
