  We present a statistical analysis of ion distributions in magnetic
reconnection jets using data from the Magnetospheric Multiscale spacecraft.
Compared with the quiet plasma in which the jet propagates, we often find
anisotropic and non-Maxwellian ion distributions in the plasma jets. We observe
magnetic field fluctuations associated with unstable ion distributions, but the
wave amplitudes are not large enough to scatter ions during the observed travel
time of the jet. We estimate that the phase-space diffusion due to chaotic and
quasi-adiabatic ion motion in the current sheet is sufficiently fast to be the
primary process leading to isotropization.

Space Physics