Migration of Fast Magnetosonic Waves in the Magnetosphere With a Plasmaspheric Plume

Plasmaspheric density structures are considered to control the propagation trajectories of fast magnetosonic (MS) waves in the inner magnetosphere. However, whether the plasmaspheric plume can effectively alter the propagation of MS waves remains unknown. Based on the analytical model of plasma density, ray tracing simulations are performed to investigate the propagation of exactly perpendicular MS waves in the equatorial plane in the magnetosphere containing a plasmaspheric plume. We find that plasmatrough and plume MS waves propagating toward the plasmaspheric plume can be reflected into the plasmaspheric core by the plume, then potentially migrating globally and thus quasi‐trapped inside the plasmaspheric core. The simulations also indicate that lower‐frequency MS waves approaching the plasmaspheric plume are more easily reflected and quasi‐trapped inside the plasmaspheric core. Our findings illustrate a previously unexplored way that plasmatrough MS waves could access and be trapped inside the plasmaspheric core via azimuthal plasmaspheric density structures. Plain Language Summary Fast magnetosonic (MS) waves are one of the most common and intense electromagnetic emissions observed both inside and outside the plasmasphere. Portions of MS waves observed inside the plasmasphere are supposed to come from the propagation of those waves outside the plasmasphere. It is well known that the radial plasmaspheric density structures can strongly alter the propagation trajectories of MS waves in the inner magnetosphere. However, a typical azimuthal plasmaspheric density structure, the plasmaspheric plume, can form in the magnetosphere during the geomagnetic disturbed times. How the plasmaspheric plume affects the propagation of MS waves remains unknown. Based on the ray tracing simulations, we show that MS waves generated outside the plasmapause and inside the plume can be reflected into the plasmaspheric core by the plasmaspheric plume and a few of the reflected waves can migrate globally inside the plasmaspheric core. Our findings provide a new potential way for MS waves to access and be trapped inside the plasmaspheric core. Key Points Propagation of magnetosonic waves in the magnetosphere containing a plasmaspheric plume is examined using the ray tracing simulations Plasmatrough and plume magnetosonic waves can be reflected into the plasmaspheric core by the plasmaspheric plume Those reflected magnetosonic waves can be quasi‐trapped inside the plasmaspheric c