Velocity Space Evolution of Dayside Reconnection Outflow

Magnetic reconnection is a universal phenomenon occurring when energy stored in a complicated magnetic field topology is released into the surrounding plasma as the field simplifies its configuration. At Earth's dayside magnetopause, reconnection is responsible for mass and energy input from the solar wind into the magnetosphere. We describe the evolution of the velocity-space evolution of plasma outflow from a dayside magnetic reconnection region. We analyze Cluster magnetopause crossings between 1 and 10 Earth radii from the reconnection X-line predicted by the maximum magnetic shear model. The effects of nonadiabatic processes, such as deformation of the profile due to finite-gyroradius-induced pitch-angle scattering and wave-particle interactions, are described. We compare observations and simulation results to describe the outflow evolution and infer the field-aligned distance between an observation and the reconnection site producing it.