ALFVÉNIC Wave Pressures and the Solar Wind

Abstract

Using a one-fluid polytrope model of the solar wind, we investigate the detailed behavior of outwardly propagating coronal Alfvén waves and their effects on the dynamics of the expanding solar corona as they propagate and are convected into interplanetary space. The waves exert an effective pressure on the solar wind, analogous to a radiation pressure, and inclusion of the energy fluxes of Alfvénic waves can result in significant changes in the large-scale streaming properties of the solar wind. Under some conditions, the coronal Alfvén waves can provide the primary energy flux needed to drive the wind. The relevance of this model to observed streaming properties of the solar wind is discussed. An attractive feature of the wave-driven solution is the ability of the waves to produce a combination of high velocities (~700 km s-1) and low densities (^2 particles cm-3) at 1 a.u. for reasonable coronal conditions at 10 6 km.