HF-pump-induced parametric instabilities in the auroral E-region

In November 1999 the EISCAT high power, high-frequency (HF) facility located near Tromsø, Norway, was used to create artificial plasma turbulence in the ionosphere. During the experiment the EISCAT 224 MHz radar and sometimes the 931 MHz radar were used to obtain measurements of incoherent scatter ion and plasma lines, and artificially enhanced spectra of E-region plasma waves were measured for the first time at auroral latitudes with both radars. During periods with suitable peak E-region electron density, Z-mode propagation of the HF pump wave to the topside E-region occured, and topside instability-enhanced plasma waves were observed. In addition to HF-pump-induced effects, an unusual F-region echo was seen in both the ion and plasma line channels, which appears to be due to an auroral arc intersecting the radar beam.