Kinetic properties of heavy solar wind ions from Ulysses-SWICS

Abstract

The kinetic properties of heavy ions in the solar wind reflect the plasma processes governing the solar wind in the heliosphere. We use Ulysses-SWICS data that resolve heavy ions in a wide range of mass-per-charge values, 2 <= m/q <= 9.33, to investigate the heavy ions and their dynamic evolution throughout the heliosphere. While at 1 AU the imprint of Coulomb collisions is known to be present in the slow solar wind, we show that is vanishes by the time the wind has reached 5 AU. All ion species flow with equal bulk and thermal speeds there. This is interpreted as a progressive dominance of wave-particle interactions over Coulomb collisions.