UCL have operated Fabry-Perot Interferometers in Arctic Scandinavia since 1980: at a polar cap site – Svalbard; and 2 auroral oval sites – Kiruna and Sodankylä. They observe red and green line airglow and auroral emissions throughout the hours of darkness; which is 24 hours from November to January at Svalbard. Measurements of Doppler shift and Doppler broadening allow determination of winds and temperatures of the thermosphere at 240-250km altitude, and 110-120km altitude, using the red and green line, respectively. The Svalbard site has a narrow field FPI and a wide field FPI called SCANDI. The latter gives a wide field-of-view with a diameter of around 1,000km, which is divided into sectors. Thus multi-point fields of wind, temperature and emission intensity are created. The field-of-view overlaps with the Hankasalmi and Pikkvibaer SuperDARN HF radars, and the EISCAT UHF radar, which has allowed a direct comparison of neutral and ion behaviour in the polar cap. This talk presents the consequences for Joule heating when the response times of the neutral gas and ionosphere are very different.
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