• Evolution of IMF By Induced Asymmetries: The Role of Tail Reconnection 

      Ohma, Anders; Østgaard, Nikolai; Laundal, Karl Magnus; Reistad, Jone Peter; Hatch, Spencer Mark; Tenfjord, Paul Arne Riksheim (Journal article; Peer reviewed, 2021)
      North-south asymmetries arise in the magnetosphere-ionosphere system when a significant east-west (By) component is present in the interplanetary magnetic field (IMF). During such conditions, a By component with the same ...
    • Exploring solar-terrestrial interactions via multiple imaging observers 

      Branduardi-Raymont, Graziella; Berthomier, M; Bogdanova, Y. V.; Carter, Jennifer; Collier, M; Dimmock, A; Dunlop, Malcolm; Fear, Robert C.; Forsyth, Colin; Hubert, Benoit; Kronberg, Elena A.; Laundal, Karl Magnus; Lester, Mark; Oksavik, Kjellmar; Østgaard, Nikolai; Palmroth, Minna; Plaschke, Ferdinand; Porter, F.S.; Rae, I. Jonathan; Read, Andy; Samsonov, A. A.; Sembay, Steven; Shprits, Yuri; Sibeck, David G.; Walsh, Brian; Yamauchi, M (Journal article; Peer reviewed, 2021)
      How does solar wind energy flow through the Earth’s magnetosphere, how is it converted and distributed? is the question we want to address. We need to understand how geomagnetic storms and substorms start and grow, not ...
    • 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 ...
    • Global Distribution of Key Features of Streamer Corona Discharges in Thunderclouds 

      Soler, S.; Gordillo-Vázquez, F.J.; Pérez-Invernón, F.J.; Luque, A.; Li, D.; Neubert, T.; Chanrion, O.; Reglero, V.; Navarro-González, J.; Østgaard, Nikolai (Journal article; Peer reviewed, 2022)
      We present nighttime worldwide distributions of key features of Blue LUminous Events (BLUEs) detected by the Modular Multispectral Imaging Array of the Atmosphere-Space Interaction Monitor. Around 10% of all detected BLUEs ...
    • Global Frequency and Geographical Distribution of Nighttime Streamer Corona Discharges (BLUEs) in Thunderclouds 

      Soler, S.; Gordillo-Vázquez, F.J.; Pérez-Invernón, F. J.; Luque, Alejandro; Li, D.; Neubert, Torsten; Chanrion, Olivier; Reglero, Victor; Navarro-Gonzalez, Javier; Østgaard, Nikolai (Journal article; Peer reviewed, 2021)
      Blue LUminous Events (BLUEs) are transient corona discharges occurring in thunderclouds and characterized by strong 337.0 nm light flashes with absent (or weak) 777.4 nm component. We present the first nighttime climatology ...
    • The Hall current system revealed as a statistical significant pattern during fast flows 

      Snekvik, Kristian; Nakamura, R.; Østgaard, Nikolai; Haaland, Stein; Retinò, A. (Peer reviewed; Journal article, 2008-11-05)
      We have examined the dawn-dusk component of the magnetic field, BY , in the night side current sheet during fast flows in the neutral sheet. 237 h of Cluster data from the plasma sheet between 2 August 2002 and 2 October ...
    • How the IMF By induces a By component in the closed magnetosphere and how it leads to asymmetric currents and convection patterns in the two hemispheres 

      Tenfjord, Paul; Østgaard, Nikolai; Snekvik, Kristian; Laundal, Karl Magnus; Reistad, Jone Peter; Haaland, Stein; Milan, Steve (Peer reviewed; Journal article, 2015-11-12)
      We used the Lyon-Fedder-Mobarry global magnetohydrodynamics model to study the effects of the interplanetary magnetic field (IMF) By component on the coupling between the solar wind and magnetosphere-ionosphere system. ...
    • The impact of sunlight on high-latitude equivalent currents 

      Laundal, Karl Magnus; Gjerløv, Jesper; Østgaard, Nikolai; Reistad, Jone Peter; Haaland, Stein; Snekvik, Kristian; Tenfjord, Paul; Ohtani, Shin-ichi; Milan, Steve (Peer reviewed; Journal article, 2016-03)
      Ground magnetic field measurements can be mathematically related to an overhead ionospheric equivalent current. In this study we look in detail at how the global equivalent current, calculated using more than 30 years of ...
    • Initiation of lightning flashes simultaneously observed from space and the ground: Narrow bipolar events 

      López, Jesús A.; Montanyà, Joan; van der Velde, Oscar; Romero, David; Gordillo-Vázquez, Francisco J.; Pérez-Invernón, Francisco J.; Luque, Alejandro; Morales Rodriguez, Carlos Augusto; Neubert, Torsten; Rison, William; Krehbiel, Paul; González, Javier Navarro; Østgaard, Nikolai; Reglero, Víctor (Journal article; Peer reviewed, 2022)
      We investigate the initiation of four lightning flashes detected from ground by means of the Colombia Lightning Mapping Array (Colombia-LMA) and simultaneously observed from space by the optical sensors of the Atmosphere-Space ...
    • Intensity asymmetries in the dusk sector of the poleward auroral oval due to IMF Bx 

      Reistad, Jone Peter; Østgaard, Nikolai; Laundal, Karl Magnus; Haaland, Stein; Tenfjord, Paul; Snekvik, Kristian; Oksavik, Kjellmar; Milan, Steve (Peer reviewed; Journal article, 2014-12)
      In the exploration of global-scale features of the Earth's aurora, little attention has been given to the radial component of the Interplanetary Magnetic Field (IMF). This study investigates the global auroral response in ...
    • Interplanetary Magnetic Field Bx Component Influence on Horizontal and Field-Aligned Currents in the Ionosphere 

      Laundal, Karl Magnus; Reistad, Jone Peter; Finlay, Christopher C.; Østgaard, Nikolai; Tenfjord, Paul; Snekvik, Kristian; Ohma, Anders (Peer reviewed; Journal article, 2018-05)
      Statistical analyses have shown that the sunward component of the interplanetary magnetic field, Bx (Geocentric Solar Magnetospheric), moderately but significantly affects the auroral intensity. These observations have ...
    • In‐Flight Observation of Positron Annihilation by ILDAS 

      Kochkin, Pavlo; Sarria, David; Skeie, Chris Alexander Kallevik; Van Deursen, Alexander P.J.; de Boer, A; Bardet, Michiel; Allasia, Cedric; Flourens, Franck; Østgaard, Nikolai (Peer reviewed; Journal article, 2018-08)
      We report a 511‐keV photon flux enhancement that was observed inside a thundercloud and is a result of positron annihilation. The observation was made with the In‐flight Lightning Damage Assessment System (ILDAS) on board ...
    • Library of Simulated Gamma-Ray Glows and Application to Previous Airborne Observations 

      Sarria, David Alexandre Stephan; Østgaard, Nikolai; Marisaldi, Martino; Lehtinen, Nikolai Grigorievich; Mezentsev, Andrey (Journal article; Peer reviewed, 2023)
      Gamma-Ray Glows (GRGs) are high energy radiation originating from thunderclouds, in the MeV energy regime, with typical duration of seconds to minutes, and sources extended over several to tens of square kilometers. GRGs ...
    • Magnetospheric response and reconfiguration times following IMF By reversals 

      Tenfjord, Paul Arne Riksheim; Østgaard, Nikolai; Strangeway, Robert J.; Haaland, Stein; Snekvik, Kristian; Laundal, Karl Magnus; Reistad, Jone Peter; Milan, Stephen Eric (Peer reviewed; Journal article, 2017-01)
      The interaction between the interplanetary magnetic field (IMF) and the geomagnetic field at the dayside magnetopause leads to transfer of momentum and energy which changes the magnetospheric configuration, but only after ...
    • Meter-scale spark X-ray spectrum statistics 

      Carlson, Brant Edward; Østgaard, Nikolai; Kochkin, Pavlo; Grøndahl, Øystein; Nisi, Ragnhild Schrøder; Weber, Kristian; Scherrer, Zack; LeCaptain, Kristian (Peer reviewed; Journal article, 2015-11-13)
      X-ray emission by sparks implies bremsstrahlung from a population of energetic electrons, but the details of this process remain a mystery. We present detailed statistical analysis of X-ray spectra detected by multiple ...
    • Modeling lightning observations from space-based platforms (CloudScat.jl 1.0) 

      Luque, Alejandro; Gordillo-Vázquez, Francisco José; Li, Dongshuai; Malagón-Romero, Alejandro; Pérez-Invernón, F. J.; Schmalzried, Anthony; Soler, Sergio; Chanrion, Olivier; Heumesser, Matthias; Neubert, Torsten; Reglero, Victor; Østgaard, Nikolai (Journal article; Peer reviewed, 2020)
      We describe a computer code that simulates how a satellite observes optical radiation emitted by a lightning flash after it is scattered within an intervening cloud. Our code, CloudScat.jl, is flexible, fully open source ...
    • Modeling the relativistic runaway electron avalanche and the feedback mechanism with GEANT4 

      Skeltved, Alexander Broberg; Østgaard, Nikolai; Gjesteland, Thomas; Celestin, Sebastien; Carlson, Brant Edward (Peer reviewed; Journal article, 2014-11)
      This paper presents the first study that uses the GEometry ANd Tracking 4 (GEANT4) toolkit to do quantitative comparisons with other modeling results related to the production of terrestrial gamma ray flashes and high-energy ...
    • The modular X- and gamma-ray sensor (MXGS) of the ASIM Payload on the International Space Station 

      Østgaard, Nikolai; Balling, Jan E.; Bjørnsen, Thomas Riis; Brauer, Peter; Budtz-Jørgensen, Carl; Bujwan, Waldemar; Carlson, Brant Edward; Christiansen, Freddy; Connell, Paul; Eyles, Chris; Fehlker, Dominik; Genov, Georgi; Grudzinski, Pawel; Kochkin, Pavlo; Kohfeldt, Anja; Kuvvetli, Irfan; Thomsen, Per Lundahl; Pedersen, Søren Møller; Navarro-Gonzalez, Javier; Neubert, Torsten; Njøten, Kåre; Orleanski, Piotr; Qureshi, Bilal Hasan; Cenkeramaddi, Linga Reddy; Reglero, Victor; Reina, Manuel; Rodrigo, Juan Manuel; Rostad, Maja Elise; Sabau, Maria D.; Kristensen, Steen Savstrup; Skogseide, Yngve; Solberg, Arne Olav; Stadsnes, Johan; Ullaland, Kjetil; Yang, Shiming (Peer reviewed; Journal article, 2019-02-18)
      The Modular X- and Gamma-ray Sensor (MXGS) is an imaging and spectral X- and Gamma-ray instrument mounted on the starboard side of the Columbus module on the International Space Station. Together with the Modular Multi-Spectral ...
    • Multi-Pulse Corona Discharges in Thunderclouds Observed in Optical and Radio Bands 

      Li, Dongshuai; Luque, Alejandro; Lehtinen, Nikolai Grigorievich; Gordillo-Vázquez, F.J.; Neubert, Torsten; Lu, Gaopeng; Chanrion, Olivier; Zhang, Hongbo; Østgaard, Nikolai; Reglero, Víctor (Journal article; Peer reviewed, 2022)
      How lightning initiates inside thunderclouds remains a major puzzle of atmospheric electricity. By monitoring optical emissions from thunderstorms, the Atmosphere-Space Interactions Monitor (ASIM) onboard the International ...