Multi-frequency SuperDARN radar observations of the modulated ionosphere by high-power radio-waves at EISCAT

Abstract

This paper presents the first joint observations of multi-frequency SuperDARN (Super Dual Auroral Radar Network) radar of the heated ionosphere by high-power high-frequency (HF) ground-based radio-waves along with the stimulated electromagnetic emissions (SEE) measurements. The unique heating experiment design at EISCAT (The European Incoherent Scatter Scientific Association) including fine frequency stepping through the fourth electron gyro-frequency (4<i>f_ce</i>) provided the opportunity to directly determine the plasma waves responsible for SuperDARN radar echoes. Past experiments using a unique Kodiak SuperDARN receiver in Alaska with capability of data recording over a large bandwidth of frequencies different from the radar transmission frequency was able to detect some radar echoes due to pump-excited plasma waves. However, a precise characterization of these waves could not be reached in the past. Comparison of the behavior of the SEE data measured on the ground besides the multi-frequency SuperDARN observations above the heated ionosphere at EISCAT has shown a good correlation with the characteristics of upper-hybrid (UH)/electron Bernstein (EB) waves excited through parametric decay instability. The ray tracing model based on the EISCAT dynasonde data of the background ionospheric parameters has been used in order to determine the natural ionospheric effects on the propagation path of 9.9 MHz, 13.2 MHz, and 16.6 MHz signals associated with SuperDARN radar. By providing a more direct connection between SuperDARN echoes and the associated SEE measurements, this new technique potentially provides more quantitative characterization of plasma waves generated during ionospheric heating.