Swarm Observations of Low-altitude Cusp Ion Upflow

Abstract:

Swarm multi-satellite measurements of electric field, ion and electron temperature, and ion upflow at 1-10 km scales are used to probe the relationship between frictional ion heating, soft particle precipitation, and ion upflow in the vicinity of Earth's low-altitude magnetic cusps. Frictional ion heating is a non-equilibrium process associated with strong convection electric fields (with strengths exceeding 20 mV/m) at F-region and lower altitudes. Heated plasma is transported upward, where it can feed efficient energization mechanisms at higher altitude leading to outflow. An additional pathway for upflow is electron heating associated with soft magnetosheath precipitation. Correlations between electric field strength, electron temperature, and ion upflow and their variabilities on scales of minutes to hours are examined to provide insight on the extent to which the frictional heating and electron heating pathways drive ion upflow at 500 km altitude.