Reinterpretation of mirror modes as trains of slow magnetosonic solitons

Abstract

It is shown that large amplitude periodic oscillations of the magnetic field measured frequently by spacecraft in the magnetosheath, and interpreted as mirror-mode waves/structures, represent trains of slow-mode magnetosonic solitons. Nonlinear magnetosonic wave-trains with properties attributed previously to mirror-mode structures are obtained as exact solutions of Hall-MHD equations with anisotropic ion pressure. The theoretically derived properties of magnetosonic solitons are compared with multipoint measurements on Cluster satellites in the magnetosheath with plasma beta (plasma/magnetic pressure) ~10. The computed properties of nonlinear waves: amplitudes, spatial scales, periodicity, and propagation velocities are consistent with in situ measurements in space.