Magnetic and Velocity Shear Driven Instabilities in the Heliospheric Plasma

We have addressed the problem of combined magnetic and velocity shear driven instabilities in the context of the heliospheric plasma. New high-order numerical methods have been used to analyze the instability dynamics of the heliospheric current-sheet interacting with the structure determined by the slow component of the solar wind on the solar equatorial plane above the helmet streamers. Preliminary results are presented.     

Hydrodynamics of the Solar Wind Expansion

A pedagogical introduction to the classical hydrodynamic steady state solutions for flows in a spherically symmetric atmosphere is presented along with a detailed analysis of the stability of such flows and a discussion of the Parker/Bondi phase diagram of solutions in the Mach number – stellar radius plane. This leads naturally to the scenario presented by Velli (1994) for wind-accretion transitions, which helps to explain results from numerical simulations in many contexts and gives a more comprehensive answer to the question of why the solar wind and other steady state flows in spherical symetry must quite generally become supersonic.