Quasi-linear modeling of gyroresonance between different MLT chorus and geostationary orbit electrons

Abstract

The contributions of dayside and nightside gyroresonance of chorus waves to electron radiation belt evolution at L = 6.6 are detailedly differentiated via fully solving the two-dimensional Fokker-Plank equation. The numerical results show that the chorus waves at different regions play significantly different roles. The dayside chorus waves can cause obvious loss of energetic electrons at lower pitch angles and weak energization at larger pitch angles. The nightside chorus waves can yield significant energization at larger pitch angles, but cannot efficiently resonate with the energetic electrons at lower pitch angle. Due to the numerical difficulty in fully solving Fokker-Planck equation, the cross diffusion terms are often ignored in the previous work. Here the effect of cross diffusion at different regions is further analyzed. On the dayside, ignoring cross diffusion overestimates the electron phase space density by several orders of magnitude at lower pitch angles, and consequently the dayside chorus waves are incorrectly regarded as an effective energization mechanism. On the nightside, ignoring cross diffusion overestimates the electron phase space density (PSD) by about one order of magnitude at larger pitch angles. These numerical results suggest that cross diffusion terms can significantly affect gyroresonance of chorus waves on both the dayside and nightside, which should be included in the future radiation belt models.