Now showing items 1-19 of 19

    • 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 (Copernicus Publications, 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 ...
      Journal article
    • 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. (Wiley, 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 ...
      Journal article
    • Can magnetotail reconnection produce the auroral intensities observed in the conjugate ionosphere? 

      Østgaard, Nikolai; Snekvik, Kristian; Borg, Anette Lauen; Åsnes, Arne; Pedersen, Arne; Øieroset, Marit; Phan, Tai D.; Haaland, Stein (American Geophysical Union, 2009-06)
      [1] In a recent case study, Borg et al. (2007) reported that an inverted V structure, caused by a field-aligned potential drop of 30 kV producing very strong X-ray aurora, was found in connection with tail reconnection. ...
      Journal article
    • Characteristics of the flank magnetopause: Cluster observations 

      Haaland, Stein; Reistad, Jone Peter; Tenfjord, Paul; Gjerloev, Jesper W.; Maes, Lukas; deKeyser, Johan; Maggiolo, Romain; Anekallu, Chrandrasehkar; Dorville, Nicolas (WileyAmerican Geophysical Union, 2014-11)
      The magnetopause is a current sheet forming the boundary between the geomagnetic field on one side and the shocked solar wind on the other side. This paper discusses properties of the low-latitude dawn and dusk flanks ...
      Journal article
    • Cluster observations of a field aligned current at the dawn flank of a bursty bulk flow 

      Snekvik, Kristian; Haaland, Stein; Østgaard, Nikolai; Hasegawa, H.; Nakamura, R.; Takada, T.; Juusola, L.; Amm, O.; Pitout, F.; Rème, H.; Klecker, B.; Lucek, E. A. (European Geosciences Union, 2007-06-29)
      This article describes observations of a bursty bulk flow (BBF) in the outer central plasma sheet. The observations are made with the Cluster satellites, located approximately 19RE downtail, close to the midnight sector ...
      Journal articlePeer reviewed
    • Dawn-dusk asymmetries in the coupled solar wind-magnetosphere-ionosphere system: a review 

      Walsh, Andrew P.; Haaland, Stein; Forsyth, Colin; Keesee, Amy M.; Kissinger, Jennifer; Li, Kun; Runov, Andrei; Soucek, Josef; Walsh, Brian M.; Wing, Simon; Taylor, Matthew G.G.T. (Copernicus Publications, 2014-07-01)
      Dawn–dusk asymmetries are ubiquitous features of the coupled solar-wind–magnetosphere–ionosphere system. During the last decades, increasing availability of satellite and ground-based measurements has made it possible to ...
      Journal article
    • 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 (American Geophysical Union, 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 ...
      Journal article
    • Distribution of energetic oxygen and hydrogen in the near-Earth plasma sheet 

      Kronberg, Elena A.; Grigorenko, Elena; Haaland, Stein; Daly, Patrick W.; Delcourt, Dominique C.; Luo, Hao; Kistler, Lynn M.; Dandouras, Iannis (Wiley, 2015-05)
      The spatial distributions of different ion species are useful indicators for plasma sheet dynamics. In this statistical study based on 7 years of Cluster observations, we establish the spatial distributions of oxygen ions ...
      Journal article
    • 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. (AGU Publications, 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 ...
      Journal article
    • Estimation of cold plasma outflow during geomagnetic storms 

      Haaland, Stein; Eriksson, A.; Maes, L.; Baddeley, Lisa; Barakat, A.; Chappell, R.; Eccles, V.; Johnsen, C.; Lybekk, Bjørn; Li, K.; Pedersen, A; Schunk, R.; Welling, D. (Wiley, 2015-12-01)
      Low-energy ions of ionospheric origin constitute a significant contributor to the magnetospheric plasma population. Measuring cold ions is difficult though. Observations have to be done at sufficiently high altitudes and ...
      Journal article
    • The Hall current system revealed as a statistical significant pattern during fast flows 

      Snekvik, Kristian; Nakamura, R.; Østgaard, Nikolai; Haaland, Stein; Retinò, A. (European Geosciences Union, 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 ...
      Journal articlePeer reviewed
    • 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 (Wiley, 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. ...
      Journal article
    • 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 (Wiley, 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 ...
      Journal article
    • 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 (WileyAmerican Geophysical Union, 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 ...
      Journal article
    • 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 (American Geophysical Union, 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 ...
      Journal article
    • 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 (American Geophysical Union, 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 ...
      Journal article
    • 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 (Springer, 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 ...
      Journal article
    • 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 (Wiley, 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 ...
      Journal article
    • Solar illumination control of ionospheric outflow above polar cap arcs 

      Maes, Lukas; Maggiolo, Romain; De Keyser, Johan; Dandouras, Iannis; Fear, Robert C.; Fontaine, Dominique; Haaland, Stein (AGU Publications, 2015-03-12)
      We measure the flux density, composition, and energy of outflowing ions above the polar cap, accelerated by quasi-static electric fields parallel to the magnetic field and associated with polar cap arcs, using Cluster. ...
      Journal article