Correlation between number flux and energy of upward flowing ion beams

A statistical study of the properties of energetic (> 0.5 keV) upward flowing ion beams observed within broad structures of parallel electric fields is presented. These events were observed rather commonly above 5000km altitude and in the dusk to midnight local time auroral region from 1976 to 1977. Within these structures, the average energies of the O + ions were typically a factor of one to three times greater than the H + ions. Hence, species dependent acceleration and/or energy loss processes were typical in large scale parallel electric field events. Although the mean ion energies and number fluxes were highly variable from one structure to another, they were nevertheless found to be statistically correlated. The correlation exists primarily with the O + flux and implies a decrease in average ion energy with increasing total upward flux of O + ions.