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.