Whistler mode chorus waves guided by plasmapause density gradient

Variations of plasma density and magnetic field have great influence on the property and distribution of chorus waves. In this letter, we demonstrate that chorus waves could be guided by plasmapause density gradient combining with the gradient of magnetic field based on NASA's Van Allen Probes (RBSP) data. The guiding effect could occur on the inner and outer edge of plasmapause. Lower-band chorus waves propagating at small wave normal angles (WNAs) could be trapped on the inner edge, and lower-band chorus waves with highly oblique WNAs could be confined by the outer edge. Notably, such guiding effect of plasmapause is fairly efficient for chorus waves, therefore has a strong effect on the distribution of chorus waves. Our study provides some new insights into understanding propagation and distribution of lower-band chorus waves in the plasmapause region.