The IIT Madras nano-satellite aims to investigate the science of energetic particle precipitation from the inner Van Allen (VA) radiation belt into the upper ionosphere as a potential precursor to earthquakes. Precursors in the form of low-frequency electromagnetic waves can appear several hours before an earthquake. These waves, captured near the ionosphere–magnetosphere transition region, propagate along geomagnetic field lines as Alfvén waves and interact resonantly with trapped energetic particles in the radiation belt, causing their precipitation. Such precipitation can be observed by satellites as energetic particle bursts occurring a few hours prior to the earthquake. A numerical study of Alfvén wave–energetic proton interactions in the inner VA belt is presented here to investigate the energetic proton precipitation and make predictions to support the scientific objective of the IITM satellite mission. A kinetic model of the energetic trapped proton population in the inner belt is developed, yielding a steady-state distribution that reproduces the observed density profile. The finite-difference time-domain method is employed to simulate both narrowband seismic event–specific emissions and broadband background noise representing magnetohydrodynamic Alfvén wave activity in the inner radiation belt. The studies of interactions of narrow-band Alfvén wave packets with the energetic protons in the belt reveals that a sharp cyclotron resonance condition arises at a low Alfvén frequency (10 Hz), causing substantial precipitation of high energy protons (125 MeV) from their stable mirror orbits. This precipitation can be clearly distinguished from background noisy interactions. Based on these results, we predict the optimal satellite orbital altitude for detecting such energetic proton bursts.
Maiti et al. (Wed,) studied this question.