Study On Propagation Characteristics Of Lightning-generated Whistler Waves

Based on the theoretical knowledge and numerical models of space physics,we investigated the propagation characteristics of lightning-generated whistler waves.The magnetosphere is formed during the interaction between the solar wind and the Earth's magnetic field.The radiation belt is one of the important areas of the Earth's magnetosphere.The increase in the flux of energetic particles in the radiation belt can cause serious damage to spacecraft.The right-handed polarized whistler waves frequency are lower than the the electron gyrofrequence.In the gyroresonance with radiation belt electrons,whistler waves either scatter electrons into the loss cone or efficiently accelerate electrons to the relativistic energy.The lightning-generated whistler waves are very important whistler mode which can potentially link the ionosphere to the radiation belts.However,based on our knowledge,little research has been done on how lightning-generated whistler waves propagate upward through the plasmapause and into the radiation belts.A three-dimensional ray tracing is an appropriate approach to evaluate lightning-generated whistler waves' upward propagation in detail.Using the ray-tracing technique,we examine the propagation behavior of lightning-generated whistler waves and show that they can travel upward into the radiation belts during higher geomagnetic activities due to the plasmapause inward compression,particularly in cases of lower wave frequencies,lower wave nornal angles and azimuthal angles.The perpendicular and parallel components of the group velocities of the lightning-generated whistler waves maintain a relatively small value inside the top of the plasmasphere but change rapidly to high values outside the plasmasphere,and the latitude of the lightning-generated whistler waves'increase as the normal angle increases.These results here further reveal a detailed picture on how LGW waves escape out of the plasmasphere and onto the radiation belts.This provides a basis for further study on the propagation and spatial distribution characteristics of this type of whistle mode wave.