• How Often Do Thermally Excited 630.0 nm Emissions Occur in the Polar Ionosphere? 

      Kwagala, Norah Kaggwa; Oksavik, Kjellmar; Lorentzen, Dag Arne; Johnsen, Magnar Gullikstad (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-17)
      This paper studies thermally excited emissions in the polar ionosphere derived from European Incoherent Scatter Svalbard radar measurements from the years 2000–2015. The peak occurrence is found around magnetic noon, where the radar observations show cusp-like characteristics. The ionospheric, interplanetary magnetic field and solar wind conditions favor dayside magnetic reconnection as the dominant ...
    • On the contribution of thermal excitation to the total 630.0 nm emissions in the northern cusp ionosphere 

      Kwagala, Norah Kaggwa; Oksavik, Kjellmar; Lorentzen, Dag Arne; Johnsen, Magnar Gullikstad (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-01-25)
      Direct impact excitation by precipitating electrons is believed to be the main source of 630.0 nm emissions in the cusp ionosphere. However, this paper investigates a different source, 630.0 emissions caused by thermally excited atomic oxygen O(1D) when high electron temperature prevail in the cusp. On 22 January 2012 and 14 January 2013, the European Incoherent Scatter Scientific Association (EISCAT) ...
    • Seasonal and solar cycle variations of thermally excited 630.0 nm emissions in the polar ionosphere 

      Kwagala, Norah Kaggwa; Oksavik, Kjellmar; Lorentzen, Dag Arne; Johnsen, Magnar Gullikstad; Laundal, Karl Magnus (Journal article; Tidsskriftartikkel; Peer reviewed, 2018)
      Solar cycle and seasonal variations have been found in the occurrence of strong thermally excited 630.0 nm emissions in the polar ionosphere. Measurements from the European Incoherent Scatter Svalbard Radar have been used to derive the thermal emission intensity. Thermally excited emissions have been found to maximize at solar maximum with peak occurrence rate of ∼40% compared to ∼2% at solar minimum. ...