Two whistler-mode waves modulation by background-level density irregularity during the recovery phase of a geomagnetic storm

The plasmasphere is a vast torus shape region of the inner magnetosphere, filled with dense (∼1−106#/cm−3) and cold (less than 10eV) ions and electrons. The outer boundary of the plasmasphere, called plasmapause, is a sharp plasma density boundary that separates closed and open drift paths for cold plasmas. Distinct plasmapause with sharp density variations are only 16% of the observed plasmapause and are preferred to occur at the post-midnight and dawnside than the duskside. Most of the plasmapause, however, is accompanied by significant density irregularities. These density irregularities are thought to play an important role in wave excitation and propagation, such as the excitation of the electromagnetic ion cyclotron (EMIC) waves and magnetosonic (MS) waves, and the propagation of EMIC wave and MS waves.