• The asymmetric geospace as displayed during the geomagnetic storm on 17 August 2001 

      Østgaard, Nikolai; Reistad, Jone Peter; Tenfjord, Paul; Laundal, Karl Magnus; Rexer, Theresa; Haaland, Stein; Snekvik, Kristian; Hesse, Michael; Milan, Stephen Eric; Ohma, Anders (Peer reviewed; Journal article, 2018-11-29)
      Previous studies have shown that conjugate auroral features are displaced in the two hemispheres when the interplanetary magnetic field (IMF) has a transverse (Y) component. It has also been shown that a BY component is ...
    • Auroral imaging as a tracer of global magnetospheric dynamics 

      Laundal, Karl Magnus (Doctoral thesis, 2010-11-12)
    • 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 ...
    • Dayside and nightside magnetic field responses at 780 km altitude to dayside reconnection 

      Snekvik, Kristian; Østgaard, Nikolai; Tenfjord, Paul; Reistad, Jone Peter; Laundal, Karl Magnus; Milan, Stephen Eric; Haaland, Stein (Peer reviewed; Journal article, 2017-02)
      During southward interplanetary magnetic field, dayside reconnection will drive the Dungey cycle in the magnetosphere, which is manifested as a two‐cell convection pattern in the ionosphere. We address the response of the ...
    • Dynamic effects of restoring footpoint symmetry on closed magnetic field lines 

      Reistad, Jone Peter; Østgaard, Nikolai; Tenfjord, Paul; Laundal, Karl Magnus; Snekvik, Kristian; Haaland, Stein; Milan, Steve; Oksavik, Kjellmar; Frey, H. U.; Grokott, A. (Peer reviewed; Journal article, 2016-05-05)
      Here we present an event where simultaneous global imaging of the aurora from both hemispheres reveals a large longitudinal shift of the nightside aurora of about 3 h, being the largest relative shift reported on from ...
    • An explicit IMF By dependence on solar wind ‐ magnetosphere coupling 

      Reistad, Jone Peter; Laundal, Karl Magnus; Ohma, Anders; Moretto, Therese; Milan, Steve (Peer reviewed; Journal article, 2019)
      Presently, all empirical coupling functions quantifying the solar wind—magnetosphere energy—or magnetic flux conversion assume that the coupling is independent of the sign of the dawn-dusk component (B𝑦) of the Interplanetary ...
    • 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 ...
    • 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 ...
    • Magnetic coordinate systems 

      Laundal, Karl Magnus; Richmond, Arthur D. (Peer reviewed; Journal article, 2017-03)
      Geospace phenomena such as the aurora, plasma motion, ionospheric currents and associated magnetic field disturbances are highly organized by Earth’s main magnetic field. This is due to the fact that the charged particles ...
    • Magnetic Effects of Plasma Pressure Gradients in the Upper F Region 

      Laundal, Karl Magnus; Hatch, Spencer Mark; Moretto, Therese (Peer reviewed; Journal article, 2019)
      The Swarm satellites fly at altitudes that at polar latitudes are generally assumed to only contain currents that are aligned with the local magnetic field. Therefore, disturbances along the main field direction are mainly ...
    • 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 ...
    • North-south asymmetries in cold plasma density in the magnetotail lobes: Cluster observations 

      Haaland, Stein; Lybekk, Bjørn; Maes, Lukas; Laundal, Karl Magnus; Pedersen, Amund; Tenfjord, Paul; Ohma, Anders; Østgaard, Nikolai; Reistad, Jone Peter; Snekvik, Kristian (Peer reviewed; Journal article, 2017-01)
      In this paper, we present observations of cold (0–70 eV) plasma density in the magnetotail lobes. The observations and results are based on 16 years of Cluster observation of spacecraft potential measurements converted ...
    • North–South Asymmetries in Earth’s Magnetic Field. Effects on High-Latitude Geospace 

      Laundal, Karl Magnus; Cnossen, Ingrid; Milan, Stephen Eric; Haaland, Stein; Coxon, John C.; Pedatella, Nick; Förster, Matthias; Reistad, Jone Peter (Peer reviewed; Journal article, 2017-03)
      The solar-wind magnetosphere interaction primarily occurs at altitudes where the dipole component of Earth’s magnetic field is dominating. The disturbances that are created in this interaction propagate along magnetic field ...
    • Observations of Asymmetric Lobe Convection for Weak and Strong Tail Activity 

      Ohma, Anders; Østgaard, Nikolai; Reistad, Jone Peter; Tenfjord, Paul; Laundal, Karl Magnus; Moretto, Therese; Haaland, Stein; Krcelic, Patrik; Milan, Stephen Eric (Journal article; Peer reviewed, 2019)
      In this study we use high‐quality convection data from the Electron Drift Instrument on board Cluster to investigate how near‐Earth tail activity affects the average convection pattern in the magnetotail lobes when the ...
    • Observations of asymmetries in ionospheric return flow during different levels of geomagnetic activity 

      Reistad, Jone Peter; Østgaard, Nikolai; Laundal, Karl Magnus; Ohma, Anders; Snekvik, Kristian; Tenfjord, Paul; Grocott, Adrian; Oksavik, Kjellmar; Milan, Steve; Haaland, Stein (Peer reviewed; Journal article, 2018-06)
      It is known that the magnetic field of the Earth's closed magnetosphere can be highly displaced from the quiet‐day configuration when interacting with the interplanetary magnetic field (IMF), an asymmetry largely controlled ...
    • Overview of solar wind - magnetosphere - ionosphere - atmosphere coupling and the generation of magnetospheric currents 

      Milan, Stephen Eric; Clausen, Lasse Boy Novock; Coxon, John Charles; Carter, Jenny A.; Walach, Maria Theresia; Laundal, Karl Magnus; Østgaard, Nikolai; Tenfjord, Paul Arne Riksheim; Reistad, Jone Peter; Snekvik, Kristian; Korth, Haje; Anderson, Brian J. (Peer reviewed; Journal article, 2017-03)
      We review the morphology and dynamics of the electrical current systems of the terrestrial magnetosphere and ionosphere. Observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) ...
    • The Relationship Between Cusp Region Ion Outflows and East-West Magnetic Field Fluctuations at 4,000-km Altitude 

      Hatch, Spencer Mark; Moretto, Therese; Lynch, Kristina A.; Laundal, Karl Magnus; Gjerloev, J.; Lund, Eric (Journal article; Peer reviewed, 2020)
      A number of interdependent conditions and processes contribute to ionospheric-origin energetic ( ∼ 10 eV to several keV) ion outflows. Due to these interdependences and the associated observational challenges, energetic ...
    • Seasonal and hemispheric asymmetries of F‐region polar cap plasma density: Swarm and CHAMP observations 

      Hatch, Spencer Mark; Haaland, Stein; Laundal, Karl Magnus; Moretto, Therese; Yau, Andrew; Bjoland, Lindis Merete; Reistad, Jone Peter; Ohma, Anders; Oksavik, Kjellmar (Journal article; Peer reviewed, 2020)
      One of the primary mechanisms of loss of Earth's atmosphere is the persistent “cold” ( urn:x-wiley:jgra:media:jgra56068:jgra56068-math-0001 20 eV) ion outflow that has been observed in the magnetospheric lobes over large ...