Browsing Bergen Open Research Archive by Author "Østgaard, Nikolai"

Now showing items 61-71 of 71

    • A Rapid Gamma-Ray Glow Flux Reduction Observed From 20 km Altitude 

      Kochkin, Pavlo; Sarria, David Alexandre Stephan; Lehtinen, Nikolai Grigorievich; Mezentsev, Andrey; Yang, Shiming; Genov, Georgi; Ullaland, Kjetil; Marisaldi, Martino; Østgaard, Nikolai; Christian, Hugh J.; Grove, J.E.; Quick, M.; Al-Nussirat, S.; Wulf, E (Journal article; Peer reviewed, 2021)
      Two gamma-ray glows were observed by a high-altitude NASA ER-2 aircraft flying at 20 km altitude over a thunderstorm in Colorado, USA. The flux of the first glow rapidly intensified and then abruptly decreased within a few ...

    • Separation and quantification of ionospheric convection sources: 1. A new technique 

      Reistad, Jone Peter; Laundal, Karl Magnus; Østgaard, Nikolai; Ohma, Anders; Haaland, Stein; Oksavik, Kjellmar; Milan, Stephen Eric (Peer reviewed; Journal article, 2019-07-04)
      This paper describes a novel technique that allows separation and quantification of different sources of convection in the high‐latitude ionosphere. To represent the ionospheric convection electric field, we use the Spherical ...

    • Separation and quantification of ionospheric convection sources: 2. The dipole tilt angle influence on reverse convection cells during northward IMF 

      Reistad, Jone Peter; Laundal, Karl Magnus; Østgaard, Nikolai; Ohma, Anders; Thomas, Evan G.; Haaland, Stein; Oksavik, Kjellmar; Milan, Stephen Eric (Peer reviewed; Journal article, 2019-07-04)
      This paper investigates the influence of Earth's dipole tilt angle on the reverse convection cells (sometimes referred to as lobe cells) in the Northern Hemisphere ionosphere during northward IMF, which we relate to ...

    • A Simultaneous Observation of Lightning by ASIM, Colombia-Lightning Mapping Array, GLM, and ISS-LIS 

      Montanyà, Joan; López, Jesús A.; Morales Rodriguez, Carlos A.; van der Velde, Oscar A.; Fabró, Ferran; Pineda, Nicolau; Navarro-Gonzalez, Javier; Reglero, Victor; Neubert, Torsten; Chanrion, Olivier; Goodman, Steven J.; Østgaard, Nikolai; Ladino-Rincon, Alfonso; Romero, David; Solà, Glòria; Horta, Ricard; Freijó, Modesto (Journal article; Peer reviewed, 2021)
      The Atmosphere-Space Interactions Monitor (ASIM) on the International Space Station (ISS) provides optical radiances and images of lightning flashes in several spectral bands. This work presents a lightning flash simultaneously ...

    • Simultaneous Observations of EIP, TGF, Elve, and Optical Lightning 

      Østgaard, Nikolai; Cummer, S.A.; Mezentsev, Andrey; Luque, Alejandro; Dwyer, J.; Neubert, Torsten; Reglero, Victor; Marisaldi, Martino; Kochkin, Pavlo; Sarria, David Alexandre Stephan; Lehtinen, Nikolai Grigorievich; Ullaland, Kjetil; Yang, Shiming; Genov, Georgi; Chanrion, Olivier; Christiansen, Freddy; Pu, Y. (Journal article; Peer reviewed, 2021)
      On February 8, 2019, the Atmosphere-Space Interaction Monitor observed a terrestrial gamma-ray flash (TGF) and an Elve from a positive intracloud (+IC) lightning during the initial breakdown stage of a lightning flash north ...

    • Spectral Analysis of Individual Terrestrial Gamma-ray Flashes Detected by ASIM 

      Lindanger, Anders; Marisaldi, Martino; Sarria, David Alexandre Stephan; Østgaard, Nikolai; Lehtinen, Nikolai Grigorievich; Skeie, Chris Alexander Kallevik; Mezentsev, Andrey; Kochkin, Pavlo; Ullaland, Kjetil; Yang, Shiming; Genov, Georgi; Carlson, Brant Edward; Köhn, Christoph; Navarro-Gonzalez, Javier; Connell, Paul H.; Reglero, Victor; Neubert, Torsten (Journal article; Peer reviewed, 2021)
      The Atmosphere-Space Interactions Monitor (ASIM) is the first instrument in space specifically designed to observe terrestrial gamma-ray flashes (TGFs). TGFs are high energy photons associated with lightning flashes and ...

    • Spectral Observations of Optical Emissions Associated With Terrestrial Gamma-Ray Flashes 

      Heumesser, Matthias; Chanrion, Olivier; Neubert, Torsten; Christian, Hugh J.; Dimitriadou, Krystallia; Gordillo-Vazquez, Francisco J.; Luque, Alejandro; Pérez-Invernón, F. J.; Blakeslee, Richard J.; Østgaard, Nikolai; Reglero, Victor; Köhn, Christoph (Journal article; Peer reviewed, 2021)
      The Atmosphere-Space Interactions Monitor measures Terrestrial Gamma-Ray Flashes (TGFs) simultaneously with optical emissions from associated lightning activity. We analyzed optical measurements at 180–230, 337, and 777.4 ...

    • The Temporal Relationship Between Terrestrial Gamma-Ray Flashes and Associated Optical Pulses From Lightning 

      Skeie, Chris Alexander Kallevik; Østgaard, Nikolai; Mezentsev, Andrey; Bjørge-Engeland, Ingrid; Marisaldi, Martino; Lehtinen, Nikolai Grigorievich; Reglero, V.; Neubert, T. (Journal article; Peer reviewed, 2022)
      We present 221 Terrestrial Gamma-ray Flashes (TGFs) and associated optical pulses observed by the Atmosphere-Space Interactions Monitor (ASIM) on board the International Space Station. The events were detected between the ...

    • Terrestrial Gamma-Ray Flashes With Accompanying Elves Detected by ASIM 

      Bjørge-Engeland, Ingrid; Østgaard, Nikolai; Mezentsev, Andrey; Skeie, Chris Alexander Kallevik; Sarria, David Alexandre Stephan; Lapierre, Jeff; Lindanger, Anders; Neubert, Torsten; Marisaldi, Martino; Lehtinen, Nikolai Grigorievich; Chanrion, Olivier; Ullaland, Kjetil; Yang, Shiming; Genov, Georgi; Christiansen, Freddy; Reglero, Victor (Journal article; Peer reviewed, 2022)
      The Atmosphere-Space Interactions Monitor was designed to monitor Terrestrial Gamma-ray Flashes (TGFs) and Transient Luminous Events (TLEs) from space, enabling the study of how these phenomena are related. In this paper, ...

    • Transition in Optical and Radio Features During the Early Development of Negative Intracloud Leader 

      Huang, Anjing; Cummer, Steven A.; Pu, Yunjiao; Chanrion, Olivier A.; Neubert, Torsten; Reglero, Victor; Østgaard, Nikolai (Journal article; Peer reviewed, 2022)
      What happens when the upward in-cloud (IC) breakdown transitions into horizontally expanding extension? Optical observations of this transition in IC lightning have not previously been reported. We identify the radio and ...

    • The true fluence distribution of terrestrial gamma flashes at satellite altitude 

      Østgaard, Nikolai; Gjesteland, Thomas; Hansen, R. S.; Collier, A. B.; Carlson, B. E. (Peer reviewed; Journal article, 2012-03-24)