• Challenges and Strategic Research Plans for Earth and Heliosphere: Research Infrastructures, Projects and Initiatives 

      Mann, Ingrid; Kauristie, Kirsti; Bamford, Ruth; McCrea, Ian; Moen, Jøran Idar; Oksavik, Kjellmar; Yamauchi, Masanori; Johnsen, Magnar Gullikstad; Turunen, Esa (Peer reviewed; Journal article, 2018-07-24)
      We describe existing research infrastructures relevant for space weather and open issues of space weather research including the need for sustainable observation networks and for high-quality data products as basis for ...
    • The Cusp as a VLF Saucer Source: First Rocket Observations of Long‐Duration VLF Saucers on the Dayside 

      Moser, Chrystal; LaBelle, James William; Hatch, Spencer Mark; Moen, Jøran Idar; Spicher, Andres; Takahashi, Toru; Kletzing, Craig A.; Bounds, Scott Randolph; Oksavik, Kjellmar; Sigernes, Fred; Yeoman, Timothy K. (Journal article; Peer reviewed, 2021)
      Auroral whistler‐mode radio emissions called saucers are of fundamental interest because they require an unusually stationary emission process in the dynamic auroral environment, and it is a mystery how that can happen in ...
    • Dayside Field-Aligned Current Impacts on Ionospheric Irregularities 

      Follestad, Anna Kristine Fæhn; Herlingshaw, Katie; Ghadjari, Hossein; Knudsen, David J.; McWilliams, Kathryn A.; Moen, Jøran Idar; Spicher, Andres; Wu, Jingjing; Oksavik, Kjellmar (Journal article; Peer reviewed, 2020)
      Global Navigation Satellite Systems (GNSS) are subject to disturbances caused by plasma irregularities in the ionosphere. Studies have suggested that in addition to the gradient drift and Kelvin‐Helmholtz instabilities, ...
    • 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 ...
    • Dynamic properties of throat aurora revealed by simultaneous ground and satellite observations 

      Chen, Xiangcai; Han, Desheng; Lorentzen, Dag Arne; Oksavik, Kjellmar; Moen, Jøran Idar; Baddeley, Lisa (Peer reviewed; Journal article, 2017-03)
      Throat aurora is defined as south-north aligned auroral arcs equatorward of the dayside cusp aurora and was suggested to be the results of cold magnetospheric plasma interaction with magnetopause reconnection, but its ...
    • Electron Density Depletion Region Observed in the Polar Cap Ionosphere 

      Bjoland, Lindis Merete; Ogawa, Y.; Løvhaug, Unni Pia; Lorentzen, Dag Arne; Hatch, Spencer Mark; Oksavik, Kjellmar (Journal article; Peer reviewed, 2021)
      This paper presents and discusses electron density depletion regions observed with the incoherent scatter EISCAT Svalbard Radar (ESR) located at 75.43°N geomagnetic latitude. The data include several decades of measurements, ...
    • 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 ...
    • GPS scintillation and irregularities at the front of an ionization tongue in the nightside polar ionosphere 

      van der Meeren, Christer; Oksavik, Kjellmar; Lorentzen, Dag Arne; Moen, Jøran Idar; Romano, Vincenzo (Peer reviewed; Journal article, 2014-10)
      In this paper we study a tongue of ionization (TOI) on 31 October 2011 which stretched across the polar cap from the Canadian dayside sector to Svalbard in the nightside ionosphere. The TOI front arrived over Svalbard ...
    • GPS Scintillations and Losses of Signal Lock at High Latitudes During the 2015 St. Patrick's Day Storm 

      Jin, Yaqi; Oksavik, Kjellmar (Peer reviewed; Journal article, 2018-09)
      We investigate the Global Positioning System (GPS) amplitude and phase scintillations during a severe geomagnetic storm on 17 March 2015. The auroral oval expanded significantly due to a strongly southward interplanetary ...
    • GPS Scintillations and TEC Variations in Association With a Polar Cap Arc 

      Wang, Yong; Cao, Zheng; Xing, Zan-Yang; Zhang, Qing-He; Jayachandran, P.T.; Oksavik, Kjellmar; Balan, Nanan; Shiokawa, Kazuo (Journal article; Peer reviewed, 2021)
      A unique example of a polar cap arc producing clear amplitude and phase scintillations in GPS L-band signals is presented using observations from an all-sky imager and a GPS receiver and a digital ionosonde at Resolute Bay ...
    • GPS scintillations associated with cusp dynamics and polar cap patches 

      Jin, Yaqi; Moen, Jøran Idar; Oksavik, Kjellmar; Spicher, Andres; Clausen, Lasse Boy Novock; Miloch, Wojciech Jacek (Peer reviewed; Journal article, 2017)
      This paper investigates the relative scintillation level associated with cusp dynamics (including precipitation, flow shears, etc.) with and without the formation of polar cap patches around the cusp inflow region by the ...
    • How Often Do Thermally Excited 630.0 nm Emissions Occur in the Polar Ionosphere? 

      Kwagala, Norah Kaggwa; Oksavik, Kjellmar; Lorentzen, Dag Arne; Johnsen, Magnar Gullikstad (Peer reviewed; Journal article, 2018-01)
      This paper studies thermally excited emissions in the polar ionosphere derived from European Incoherent Scatter Svalbard radar measurements from the years 2000–2015. The peak occurrence is found around magnetic noon, where ...
    • In-flight calibration of NOAA POES proton detectors - Derivation of the MEPED correction factors 

      Sandanger, Marit Irene; Ødegaard, Linn-Kristine Glesnes; Tyssøy, Hilde Nesse; Stadsnes, Johan; Søraas, Finn; Oksavik, Kjellmar; Aarsnes, Kjell (Peer reviewed; Journal article, 2015-11-25)
      The MEPED instruments on board the NOAA POES and MetOp satellites have been continuously measuring energetic particles in the magnetosphere since 1978. However, degradation of the proton detectors over time leads to an ...
    • 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 ...
    • Multiple transpolar auroral arcs reveal insight about coupling processes in the Earth’s magnetotail 

      Zhang, Qing-He; Zhang, Yong-Liang; Wang, Chi; Lockwood, Michael; Yang, Hui-Gen; Tang, Bin-Bin; Xing, Zan-Yang; Oksavik, Kjellmar; Lyons, Larry R.; Ma, Yu-Zhang; Zong, Qiu-Gang; Moen, Jøran Idar; Xia, Li-Dong (Journal article; Peer reviewed, 2020)
      A distinct class of aurora, called transpolar auroral arc (TPA) (in some cases called “theta” aurora), appears in the extremely high-latitude ionosphere of the Earth when interplanetary magnetic field (IMF) is northward. ...
    • 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 ...