What is a characteristic of VHF signals received via auroral backscatter?

VHF signals received via auroral backscatter are characterized by significant distortion and variability in signal strength due to the unique propagation conditions caused by the aurora borealis. When VHF signals travel through the ionized particles of the aurora, the interaction can lead to changes in the phase and amplitude of the signals, resulting in a fluctuating and distorted reception. This phenomenon is due to the nature of how the signals are reflected off the auroral particles and the overall chaotic environment of the auroral region, which affects the clarity and consistency of the received signals.

The other options present characteristics that do not typically apply to VHF signals received through this method. For instance, while signals can be received over long distances, the specific attribute tied to auroral backscatter primarily involves distortion and variability rather than just range. The occurrence of auroral conditions isn't limited to winter nights, as auroras can happen any time there's sufficient solar activity, and direction-related strength can vary based on several factors, not just westward antenna orientation.