Correlation between electron and proton fluxes in postbreakup aurora

Simultaneous measurements of the electron and proton spectrum between 2 and 30 kev in the recovery phase of a large auroral substorm are reported. The proton spectrum has a power law form E−r with r varying from 2.1 to 2.9, and proton intensities are strongest at pitch angles near 90° above the atmosphere. Below 200 km the pitch angle distribution tends to isotropy, thus implying significant pitch angle scattering. Increases in the proton intensity are correlated with increases in the electron intensity. While the proton spectrum softens the electron spectrum hardens. These features are similar to the features of a precipitation mechanism proposed by Swift, which accelerates electrons at the expense of the energy of ring current protons.