Fluid versus simulation model of solitons in solar wind: Application to Ulysses observations

Abstract

This paper continues recent efforts based on Hall‐MHD theory (Sauer et al., 2007) to explain a new class of magnetically compressive solitary structures in the interplanetary space, observed by the Ulysses magnetometer (Rees et al., 2006). The theoretical basis is extended by a kinetic approach via one‐dimensional hybrid code simulations which reveal deficiencies of fluid theory in describing slow mode‐type solitons in a collisionless finite β plasma. Kinetic solitary structures, resembling obliquely propagating Alfven wave pulses with quasi‐circular or banana‐type polarization are presented which may reproduce most of the observational features. This suggests that the soliton picture provides an adequate theoretical concept for the observed events.