• Birkeland current effects on high-latitude ground magnetic field perturbations 

      Laundal, Karl Magnus; Haaland, Stein; Lehtinen, Nikolai; Gjerløv, Jesper; Østgaard, Nikolai; Tenfjord, Paul; Reistad, Jone Peter; Snekvik, Kristian; Milan, Steve; Ohtani, Shin-ichi; Anderson, Brian J. (Peer reviewed; Journal article, 2015-09-18)
      Magnetic perturbations on ground at high latitudes are directly associated only with the divergence-free component of the height-integrated horizontal ionospheric current, J⊥,df. Here we show how J⊥,df can be expressed as ...
    • Constraints on Recoil Leader Properties Estimated from X-ray Emissions in Aircraft-Triggered Discharges 

      Skeie, Chris Alexander; Østgaard, Nikolai; Lehtinen, Nikolai; Sarria, David; Kochkin, Pavlo; de Boer, Boer; Bardet, M.; Allasia, C.; Flourens, F. (Journal article; Peer reviewed, 2020)
      During Airbus aircraft campaigns flying into thunderstorms in 2014–2016, X-rays were observed during two stages of aircraft-triggered lightning: nanosecond pulses of X-rays associated with negative leader steps and bursts ...
    • Constraints to do realistic modeling of the electric field ahead of the tip of a lightning leader 

      Skeltved, Alexander Broberg; Østgaard, Nikolai; Mezentsev, Andrey; Lehtinen, Nikolai; Carlson, Brant Edward (Peer reviewed; Journal article, 2017-08)
      Several computer models exist to explain the observation of terrestrial gamma‐ray flashes (TGFs). Some of these models estimate the electric field ahead of lightning leaders and its effects on electron acceleration and ...
    • First 10 Months of TGF Observations by ASIM 

      Østgaard, Nikolai; Neubert, Torsten; Reglero, Victor; Ullaland, Kjetil; Yang, Shiming; Genov, Georgi; Marisaldi, Martino; Mezentsev, Andrey; Kochkin, Pavlo; Lehtinen, Nikolai; Sarria, David; Qureshi, Bilal Hasan; Solberg, Arne Olav; Maiorana, Carolina; Albrechtsen, Kjetil; Budtz-Jørgensen, Carl; Kuvvetli, Irfan; Christiansen, Freddy; Chanrion, Olivier; Heumesser, Matthias; Navarro-Gonzalez, Javier; Connell, Paul H.; Eyles, Christopher J; Christian, Hugh J.; Al-Nussirat, Samer (Peer reviewed; Journal article, 2019)
      The Atmosphere‐Space Interactions Monitor (ASIM) was launched to the International Space Station on 2 April 2018. The ASIM payload consists of two main instruments, the Modular X‐ray and Gamma‐ray Sensor (MXGS) for imaging ...
    • Gamma Ray Glow Observations at 20-km Altitude 

      Østgaard, Nikolai; Christian, Hugh J.; Grove, J. Eric; Sarria, David; Mezentsev, Andrey; Kochkin, Pavlo; Lehtinen, Nikolai; Quick, Mason; Al-Nussirat, Samer; Wulf, Eric; Genov, Georgi; Ullaland, Kjetil; Marisaldi, Martino; Yang, Shiming; Blakeslee, Richard J. (Peer reviewed; Journal article, 2019)
      In the spring of 2017 an ER‐2 aircraft campaign was undertaken over continental United States to observe energetic radiation from thunderstorms and lightning. The payload consisted of a suite of instruments designed to ...