Observations of aspect sensitive SPEAR-induced enhancements in incoherent scatter spectra

Dhillon, R., Robinson, T. and Yeoman, T.

University of Leicester, Leicester, UK

RF-induced plasma instabilities excited by the Space Plasma Exploration by Active Radar (SPEAR) facility give rise to characteristic spectral enhancements in incoherent scatter spectra recorded by the EISCAT Svalbard Radar (ESR), which is collocated with SPEAR. The SPEAR-induced ion and plasma line enhancements are consistent with excitation of both the purely growing mode and the parametric decay instability. The aspect sensitivity of these enhancements provides valuable information regarding the physical processes that occur within the SPEAR-affected ionospheric patch. We present observations of spectral enhancements from several directions in the magnetic meridian plane, centred on field-aligned. These direction-dependent signatures exhibit significant variability and help shed light on possible coupling between artificial field-aligned irregularities generated at the upper-hybrid height and SPEAR-induced instabilities excited near the reflection height for O-mode-polarized radio waves.