James F. Drake
University of Maryland
Ion pickup and acceleration in magnetic reconnection exhausts
Energetic ions are produced during reconnection events in the solar atmosphere, the Earth's magnetosphere and in laboratory fusion experiments. We find that during magnetic reconnection ion acceleration occurs primarily as ions cross from upstream into the Alfvenic reconnection exhaust. Depending on the strength of the guide field, protons and higher mass particles behave like pickup particles in that they abruptly cross a narrow boundary layer and find themselves in a region of Alfvenic outflow. Their motion then mimics that of a classic pickup ion, gaining an Alfvenic ExB flow in the jet and a thermal speed close to the Alfven speed. The resulting ion energy is therefore proportional to mass as in many of the solar energetic particle observations. Preliminary analysis of Wind in-situ observations of solar wind reconnection exhausts supports this picture. A model of solar energetic ion production based on multiple encounters with reconnection exhausts is being pursued.