Distribution of solar wind angular momentum between particles and magnetic field: Inferences about the Alfvén critical point from Helios observations

Abstract

We first discuss theoretically the relative importance and the behavior of the two basic terms adding to the total angular momentum flux, the angular momentum of the particles (electrons, protons and alpha particles) and of the magnetic field stresses, respectively. Second, we analyze these two quantities with respect to their dependence on heliocentric distance by using the Helios 1 and 2 plasma and interplanetary magnetic field observations between 0.3 and 1 AU classified according to low‐speed (<400 km s−1), intermediate (400–600 km s−1), and high‐speed (>600 km s−1) solar wind for the 1975–1976 epoch. Applying now these results as well as various combinations of the constants of motion for the solar wind (such as the total angular momentum flux, the mass flux, and the magnetic flux) and their observational constraints, as deduced earlier by Marsch and Richter (1984), we finally present various methods (1) to derive the values of several characteristic solar wind plasma and magnetic field parameters at the Alfvén critical points, (2) to estimate their locations above the solar surface, and (3) to obtain the radial slope of the associated solar wind velocity profiles for the three solar wind classes separately.