Unambiguous evidence of HF pump‐enhanced airglow at auroral latitudes

Abstract

Simultaneous observations by up to three low‐light imaging stations belonging to the Auroral Large Imaging System (ALIS) have provided the first strong evidence of high‐frequency (HF) pump‐enhanced airglow at auroral latitudes. The airglow was enhanced by an ordinary mode 4.04 MHz electromagnetic wave with an effective radiated power (ERP) of about 210 MW that was transmitted from the EISCAT‐Heating facility near Tromsø, Norway. While often observed at low or mid‐latitudes, and despite numerous earlier experiments, no unambiguous observations of pump‐enhanced airglow have been reported at auroral latitudes. On February 16, 1999, the first successful results were obtained, and this paper concentrates on discussing optical data from this event. Triangulated estimations of the altitude and position of the enhanced airglow are also presented. Auroral‐latitude observations of HF pump‐enhanced airglow are important in order to better understand the underlying excitation mechanisms.