Blar i Bergen Open Research Archive på forfatter "Oksavik, Kjellmar"

Viser treff 21-40 av 45

    • Observational evidence for throat aurora being associated with magnetopause reconnection 

      Han, De-Sheng; Xu, Tong; Jin, Yaqi; Oksavik, Kjellmar; Chen, Xiangcai; Liu, Jian-Jun; Zhang, Qinghe; Baddeley, Lisa; Herlingshaw, Katie (Peer reviewed; Journal article, 2019)
      Throat auroras have been suggested to be related to indentations on the subsolar magnetopause. However, the indentation generation process and the resulting ionospheric responses have remained unknown. An EISCAT Svalbard ...

    • 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 ...

    • On the contribution of thermal excitation to the total 630.0 nm emissions in the northern cusp ionosphere 

      Kwagala, Norah Kaggwa; Oksavik, Kjellmar; Lorentzen, Dag Arne; Johnsen, Magnar Gullikstad (Peer reviewed; Journal article, 2017-01)
      Direct impact excitation by precipitating electrons is believed to be the main source of 630.0 nm emissions in the cusp ionosphere. However, this paper investigates a different source, 630.0 emissions caused by thermally ...

    • On the Production of Ionospheric Irregularities Via Kelvin-Helmholtz Instability Associated with Cusp Flow Channels 

      Spicher, Andres; Deshpande, Kshitija; Jin, Yaqi; Oksavik, Kjellmar; Zettergren, Matthew D.; Clausen, Lasse Boy Novock; Moen, Jøran Idar; Hairston, Marc R.; Baddeley, Lisa (Journal article; Peer reviewed, 2020)
      We present a multi‐instrument multiscale study of a channel of enhanced, inhomogeneous flow in the cusp ionosphere occurring on November 30, 2014. We provide evidence that strong Global Navigation Satellite System (GNSS) ...

    • Overview of the Rocket Experiment for NeutralUpwelling Sounding Rocket 2 (RENU2) 

      Lessard, Marc R.; Fritz, Bruce; Sadler, Brent; Cohen, Ian J.; Kenward, David; Godbole, Niharika; Clemmons, James H.; Hecht, James H.; Lynch, Kristina A.; Harrington, Meghan; Roberts, Thomas M.; Hysell, David; Crowley, Geoff; Sigernes, Fred; Syrjäsuo, Mikko; Ellingsen, Pål Gunnar; Partamies, Noora; Moen, Jøran Idar; Clausen, Lasse Boy Novock; Oksavik, Kjellmar; Yeoman, Timothy (Journal article; Peer reviewed, 2020)
      The Rocket Experiment for Neutral Upwelling 2 (RENU2) rocket was launched on 13 December 2015 at 07:34 UT. The payload transited the cusp region during a neutral upwelling event, supported by a comprehensive set of onboard ...

    • Plasma density gradients at the edge of polar ionospheric holes: the absence of phase scintillation 

      Jenner, Luke A.; Wood, Alan G.; Dorrian, Gareth D.; Oksavik, Kjellmar; Yeoman, Timothy; Fogg, Alexandra R.; Coster, Anthea J. (Journal article; Peer reviewed, 2020)
      Polar holes were observed in the high-latitude ionosphere during a series of multi-instrument case studies close to the Northern Hemisphere winter solstice in 2014 and 2015. These holes were observed during geomagnetically ...

    • The refractive and diffractive contributions to GPS signal scintillation at high latitudes during the geomagnetic storm on 7-8 September 2017 

      Zheng, Yuhao; Xiong, Chao; Jin, Yaqi; Liu, Dun; Oksavik, Kjellmar; Xu, Chunyu; Zhu, Yixun; Gao, Shunzu; Wang, Fengjue; Wang, Hui; Yin, Fan (Journal article; Peer reviewed, 2022)
      Different indices have been used to reflect, or monitor the ionospheric scintillation, e.g. the detrended carrier phase, σφ, S4, the rate of change of the vertical total electron content index (vROTI), as well as the ...

    • The science case for the EISCAT_3D radar 

      McCrea, Ian W.; Aikio, Anita; Alfonsi, Lucilla; Belova, Evgenia; Buchert, Stephan C.; Clilverd, Mark; Engler, Norbert; Gustavsson, Björn Johan; Heinselman, C.; Kero, Johan; Kosch, Mike; Lamy, Herve; Leyser, Thomas; Ogawa, Yasunobu; Oksavik, Kjellmar; Pellinen-Wannberg, Asta; Pitout, Frederic; Rapp, Markus; Stanislawska, Iwona; Vierinen, Juha (Peer reviewed; Journal article, 2015-07-29)
      The EISCAT (European Incoherent SCATer) Scientific Association has provided versatile incoherent scatter (IS) radar facilities on the mainland of northern Scandinavia (the EISCAT UHF and VHF radar systems) and on Svalbard ...

    • Scintillation and irregularities from the nightside part of a Sun-aligned polar cap arc 

      van der Meeren, Christer; Oksavik, Kjellmar; Lorentzen, Dag Arne; Paxton, Larry J.; Clausen, Lasse Boy Novock (Peer reviewed; Journal article, 2016-06-18)
      In this paper we study the presence of irregularities and scintillation in relation to the nightside part of a long-lived, Sun-aligned transpolar arc on 15 January 2015. The arc was observed in DMSP UV and particle data ...

    • Scintillation and loss of signal lock from poleward moving auroral forms in the cusp ionosphere 

      Oksavik, Kjellmar; van der Meeren, Christer; Lorentzen, Dag Arne; Baddeley, Lisa; Moen, Jøran Idar (Journal article, 2015-10-27)
      We present two examples from the cusp ionosphere over Svalbard, where poleward moving auroral forms (PMAFs) are causing significant phase scintillation in signals from navigation satellites. The data were obtained using a ...

    • 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 ...

    • Seasonal and Solar Cycle Variations of Thermally Excited 630.0 nm Emissions in the Polar Ionosphere 

      Kwagala, Norah Kaggwa; Oksavik, Kjellmar; Lorentzen, Dag Arne; Johnsen, Magnar Gullikstad; Laundal, Karl Magnus (Peer reviewed; Journal article, 2018-08)
      Solar cycle and seasonal variations have been found in the occurrence of strong thermally excited 630.0 nm emissions in the polar ionosphere. Measurements from the European Incoherent Scatter Svalbard Radar have been used ...

    • 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 ...

    • Severe and localized GNSS scintillation at the poleward edge of the nightside auroral oval during intense substorm aurora 

      van der Meeren, Christer; Oksavik, Kjellmar; Lorentzen, Dag Arne; Rietveld, Michael T.; Clausen, Lasse Boy Novock (Peer reviewed; Journal article, 2015-12)
      In this paper we study how GPS, GLONASS, and Galileo navigation signals are compromised by strong irregularities causing severe phase scintillation (σϕ>1) in the nightside high-latitude ionosphere during a substorm on 3 ...

    • Simultaneous observations of traveling convection vortices: Ionosphere-thermosphere coupling 

      Kim, Hyomin; Lessard, Marc R.; Jones, Sarah L.; Lynch, Kristina A.; Fernandes, Philip A.; Aruliah, Anasuya L.; Engebretson, Mark J.; Moen, Jøran Idar; Oksavik, Kjellmar; Yahnin, Alexander G.; Yeoman, Timothy K. (Peer reviewed; Journal article, 2017-05)
      We present simultaneous observations of magnetosphere-ionosphere-thermosphere coupling over Svalbard during a traveling convection vortex (TCV) event. Various spaceborne and ground-based instruments made coordinated ...

    • Simultaneous rocket and scintillation observations of plasma irregularities associated with a reversed flow event in the cusp ionosphere 

      Jin, Yaqi; Moen, Jøran Idar; Spicher, Andres; Oksavik, Kjellmar; Miloch, Wojciech Jacek; Clausen, Lasse Boy Novock; Pożoga, Mariusz; Saito, Yoshifumi (Peer reviewed; Journal article, 2019-08-02)
      We present an overview of the ionospheric conditions during the launch of the Investigation of Cusp Irregularities 3 (ICI‐3) sounding rocket. ICI‐3 was launched from Ny‐Ålesund, Svalbard, at 7:21.31 UT on 3 December 2011. ...

    • Space and atmospheric physics on Svalbard: a case for continued incoherent scatter radar measurements under the cusp and in the polar cap boundary region 

      Baddeley, Lisa; Lorentzen, Dag Arne; Haaland, Stein Egil; Heino, Erkka Petteri; Mann, Ingrid Brigitte; Miloch, Wojciech Jacek; Oksavik, Kjellmar; Partamies, Noora; Spicher, Andres; Vierinen, Juha-Pekka (Journal article; Peer reviewed, 2023)
      Incoherent scatter radars (ISRs) represent the only instrument (both ground and space based) capable of making high temporal and spatial resolution measurements of multiple atmospheric parameters—such as densities, ...

    • A space hurricane over the Earth’s polar ionosphere 

      Zhang, Qing-He; Zhang, Yong-Liang; Wang, Chi; Oksavik, Kjellmar; Lyons, Larry R.; Lockwood, Michael; Yang, Hui-Gen; Tang, Bin-Bin; Moen, Jøran Idar; Xing, Zan-Yang; Ma, Yu-Zhang; Wang, Xiang-Yu; Ning, Ya-Fei; Xia, Li-Dong (Journal article; Peer reviewed, 2021)
      In Earth’s low atmosphere, hurricanes are destructive due to their great size, strong spiral winds with shears, and intense rain/precipitation. However, disturbances resembling hurricanes have not been detected in Earth’s ...

    • Space weather challenges of the polar cap ionosphere 

      Moen, Jøran Idar; Oksavik, Kjellmar; Alfonsi, Lucilla; Dåbakk, Yvonne Rinne; Romano, Vineenzo; Spogli, Luca (Peer reviewed; Journal article, 2013)
      This paper presents research on polar cap ionosphere space weather phenomena conducted during the European Cooperation in Science and Technology (COST) action ES0803 from 2008 to 2012. The main part of the work has been ...