Blar i Bergen Open Research Archive på forfatter "Snekvik, Kristian"
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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 ... -
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 ... -
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 (Peer reviewed; Journal article, 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. ... -
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. (Peer reviewed; Journal article, 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 ... -
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 ... -
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 ... -
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 ... -
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 ... -
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 ... -
Observations of field aligned currents in the plasma sheet. Two kinds of field aligned currents generated during magnetotail convection
Snekvik, Kristian (Doctoral thesis, 2009-05-08) -
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) ...