Evolution Of Outer Radiation Belt Electrons Induced By Chorus And Hiss Waves In Different Regions

Radiation belt is the most dangerous regions of terrestrial space. It consists of two parts: theinner and the outer radiation belts. The inner belt is primarily occupied by energetic protonswhile the outer belt is mainly occupied by energetic electrons. Currently, most orbitingsatellites are moving in this space. When spacecrafts encounter energetic electrons or protons,energetic particles can yield serious risks to electronic devices and to astronauts. Hence, ithas important significances to study dynamic evolutions of the outer radiation belt. Previousworks have shown that the outer radiation belt changes dramatically during the geomagneticdisturbance. Fluxes of the outer radiation belt energetic electrons vary by an order of10-103from several minutes to several days. However, why can electrons with energies of tens orhundreds keV be accelerated to relativistic electrons? To find out this, some mechanisms havebeen proposed to account for the complicated and dramatic variation of electron radiationbelts, such as adiabatic transport, radial diffusion and wave-particle interaction. Here, wefocus on how cyclotron wave-particle interaction influences variation in the distributionfunction of energetic electrons in the outer radiation.We at first study differences betweens diffusion coefficients of dayside and nightsidechorus waves and then simulate phase space density (PSD) evolution driven by chorus waveson the two sides. Numerical results have shown that dayside and nightside chorus waves playdifferent roles in gyroresonance with energetic electrons. The dayside chorus waves causeobvious loss of energetic electrons at lower pitch angles but weak energization at larger pitchangles. The nightside chorus waves yield significant energization at larger pitch angles, butcannot efficiently resonate with the energetic electrons at lower pitch angle. We alsoinvestigate gyroresonance between energetic electrons and parallel propagating whistler-modehiss waves. The results demonstrate that hiss waves can yield PSD decrement of electronswith larger pitch angle, driving electrons to loss cone then precipitation. Finally, we checkcombined contributions of dayside chorus, nightside chorus and hiss waves to PSD evolution.We have found that gyroresonance between whistler-mode waves and electrons can primarily accelerate lower energy electrons to relativistic electrons during the recovery phases ofgeomagnetic storms. Furthermore, our results reveal that neglecting cross diffusion termsproduces overestimate in PSD evolution, indicating that cross terms can not simply ignored infuture simulating works.