Auroral electrojet parameters measured by the Chatanika incoherent scatter radar have been compared with VHF backscatter observed in a comparable spatial area by the 50-MHz auroral radar located at Anchorage. We find that D region absorption, occurring in concert with the morning (westward) electrojet, can significantly decrease the observed scatter amplitude. If the amplitude is corrected for absorption effects, we find that the scatter varies approximately linearly with either eastward or westward current density with the same slope for both periods. A surprising result is that at times, relatively large north-south current densities do not give rise to detectable backscatter. The Chatanika electric field measurements indicate that during the morning period, substantial backscatter amplitudes occur for southward fields of only 10 mV/m. In contrast, during the evening period the backscatter amplitude is zero or very low until the northward field is at least 25 mV/m. This indicates that most of the auroral backscatter that we observe in the evening period occurs under conditions when the two-stream plasma instability may be operative. However, in the morning period the backscattering irregularities are strongly generated under conditions associated with either gradient drift or two-stream instabilities.