Ion energization by ELF wave packets formed of lightning-induced emission in the low-altitude magnetosphere



We investigate a new type of resonant interaction between suprathermal ions and specific wave packets of ion cyclotron waves in which a spatially dependent wave frequency is close to the local ion cyclotron frequency, while the magnitude of the wave vector at a local point increases linearly with time. We argue that such wave packets are naturally formed of lightning-induced emission. This type of resonant wave-particle interaction, which has not been considered so far, appears to be very efficient and to result in essential consequences for both particles and waves, namely, a strong nondiffusive particle energization and simultaneous wave absorption. Since lightning strokes happen persistently over the terrestrial globe, the mechanism suggested in this paper constitutes a continual means of ion energization in the near-Earth space.