Off?Equatorial Source of Magnetosonic Waves Extending Above the Lower Hybrid Resonance Frequency in the Inner Magnetosphere

Inner magnetospheric magnetosonic waves are usually considered to grow from the near-equatorial ion Bernstein instability below lower hybrid resonance frequency and contribute significantly radiation belt electron dynamics. We here present unusual observations of extending above local in midlatitude ?15° plasmasphere after substorm proton injection. Linear analyses ray-tracing simulations show that, because latitudinal variation normal angles, these have little growth near equator but amplified accumulatively observable level over broad latitudes |?| < 30° during bounce-drift propagation. Our data modeling illustrate a previously unexplored scenario that off-equatorial ring distributions could be significant source inner magnetosphere. Such off-equatorially generated might differ near-equatorially ones coverage, wavevector distribution, then effect on electrons.