DAYSIDE AURORAL HYDROGEN EMISSION AS AN AERONOMIC SIGNATURE OF MAGNETOSPHERIC BOUNDARY-LAYER PROCESSES

Doppler spectral profiles of dayside auroral hydrogen show sudden incr eases in precipitating proton energy by a broadening of the spectral p rofile towards shorter wavelengths. This coincides with the equatorwar d motion of the dayside aurora. A model of the expected spectral chara cter and spatial distribution of the H emission shows that the H emiss ion spectrum is a direct measure of the reconnection process at the da yside magnetopause, i.e., 1) the narrow, symmetric spectral profiles a re a measure of the magnetospheric ''velocity filter'', 2) the sudden spectral shift of the H emission profiles reflect changes of ion energ y due to an increase in the rate of reconnection, 3) spectral H emissi on observations could be used to map the spatial distribution of the p recipitating ion energy, the total reconnection rate, the reconnection sites on the magnetopause, and the direction and intensity of convect ion.