High‐frequency magnetospheric sounding at EISCAT: Some trials and their implications

Abstract

[1] The results of some recent experiments employing the EISCAT HF ''heating'' facility at Ramfjordmoen, near Tromsø, Norway as a HF radar transmitter are described. The motivation for the experiments was the detection of ''conjugate echoes'' caused by geomagnetic field-aligned ducting of the HF wave in the magnetosphere and reflection from the magnetically conjugate ionosphere. No such echoes were detected during the experiments, which is probably to be expected from consideration of the plasma density gradients required to sustain guidance of the waves at the low HF frequencies involved. However, echoes were obtained at ranges which could be consistent with backscattering from ionospheric irregularities in the equatorial and southern auroral regions; this is similar to spread-Doppler clutter observed by large over-the-horizon radar (OTHR) systems. The experimental technique is described and the results discussed with a view toward future attempts to sound the lower magnetosphere using high-power HF transmitters.

New capabilities of the upgraded EISCAT high‐power HF facility

“…The echoes at around 1000 km are most likely from ground scatter through antenna sidelobes, as seen in earlier attempts by Senior et al . [], who also discuss other sources of echoes that are not magnetospheric. A detailed discussion of such echoes as seen by the Super Dual Auroral Radar Network radars and their use in detecting atmospheric gravity waves is given by Samson et al .…”

Past, Present and Future of Active Radio Frequency Experiments in Space

“…If similar echoes were obtained at 8 MHz corresponding to 38 m wave structures, from along the magnetic field line at high altitude, it would provide a new wavelength to study these still-poorly understood echoes which are connected with the aurora and in particular the auroral acceleration region. First attempts were made by Senior et al [2008] using the HF facility as a transmitter and a simple dipole as receiving antenna. A more sensitive system with direction finding in the north-south plane is now available.…”