• The 16-day planetary waves: multi-MF radar observations from the arctic to equator and comparisons with the HRDI measurements and the GSWM modelling results 

      Luo, Y.; Hall, Chris; Manson, A.H.; Meek, C.E.; Meyer, C.K.; Burrage, M.D.; Fritts, D.C.; Hocking, W.K.; MacDougall, J.; Riggin, D.M.; Vincent, R.A. (Journal article; Peer reviewed; Tidsskriftartikkel, 2002)
      The mesospheric and lower thermospheric (MLT) winds (60–100 km) obtained by multiple MF radars, located from the arctic to equator at Tromsø (70° N, 19° E), Saskatoon (52° N, 107° W), London (43° N, 81° W), Hawaii (21° N, 157° W) and Christmas Island (2° N, 157° W), respectively, are used to study the planetary-scale 16-day waves. Based on the simultaneous observations (1993/1994), the variabilities ...
    • Altitude calibration of the Tromsø medium frequency radar 

      Hall, Chris; Husøy, Bjørn Ove (Research report; Forskningsrapport, 2004)
      Although the Tromsø Medium Frequency Radar situated at Ramfjordmoen, Norway (69°N, 19°E) has been operating for over a quarter of a century, no definitive altitude calibration has ever been documented using independent measurements of the same atmosphere. Here we perform calibrations using the recently installed (November 2003) Nippon/Norway Tromsø Meteor Radar by identifying wind features in ...
    • An analogy to the Reynolds number for the neutral gas component of a weak plasma 

      Hall, Chris (Journal article; Peer reviewed; Tidsskriftartikkel, 2001)
      The Reynolds number Re is used as a metric to assess whether or not a flow may contain turbulence. In a weakly ionised gas with an external electric field imposed, ions exert a drag on the neutral particles. Thus, a component of the neutral motion is attributable to the ion-drag. An analogy to Re has been proposed in which the ion-drag-induced velocity contribution to the neutral motion is used. ...
    • Arctic tidal characteristics at Eureka (80 degrees N, 86 degrees W) and Svalbard (78 degrees N, 16 degrees E) for 2006/07 : seasonal and longitudinal variations, migrating and non-migrating tides 

      Hall, Chris; Manson, Alan; Meek, Chris; Chshyolkova, Tatyana; Xu, X.; Aso, Takehiko; Drummond, J. R.; Hocking, Wayne; Jacobi, Ch.; Tsutsumi, Masaki; Ward, W. (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)
    • The auroral red line polarisation: modelling and measurements 

      Lilensten, J.; Bommier, V.; Barthelemy, M; Lamy, Herve; Bernard, D; Moen, Jøran Idar; Johnsen, Magnar Gullikstad; Løvhaug, Unni Pia; Pitout, Frederic (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-08-12)
      In this work, we model the polarisation of the auroral red line using the electron impact theory developed by Bommier et al. (2011). This theory enables the computation of the distribution of the Degree of Linear Polarisation (DoLP) as a function of height if the flux of precipitated electrons is provided as input. An electron transport code is used to infer the stationary electron flux at each ...
    • A case study of gravity wave dissipation in the polar MLT region using sodium LIDAR and radar data 

      Takahashi, Toru; Nozawa, Satonori; Tsutsumi, Masaki; Hall, Chris; Suzuki, Shin; Tsuda, Takuo T.; Kawahara, Takuya D.; Saito, Norihito; Oyama, Shinichiro; Wada, Satoshi; Kawabata, Tetsuya; Fujiwara, Hitoshi; Brekke, Asgeir; Manson, Alan; Meek, Chris; Fujii, Ryoichi (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
    • A case study on generation mechanisms of a sporadic sodium layer above Tromsø (69.6° N) during a night of high auroral activity 

      Takahashi, Toru; Nozawa, Satonaori; Tsuda, Takuo T.; Ogawa, Yasunobu; Saito, Norihito; Hidemori, Takehiro; Kawahara, Takuya D.; Hall, Chris; Fujiwara, Hitoshi; Matuura, Nobuo; Brekke, Asgeir; Tsutsumi, Masaki; Wada, Satoshi; Kawabata, Tetsuya; Oyama, Shinichiro; Fujii, Ryoichi (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-08-05)
      We have quantitatively evaluated generation mechanisms of a sporadic sodium layer (SSL) based on observational data obtained by multiple instruments at a high-latitude station: Ramfjordmoen, Tromsø, Norway (69.6° N, 19.2° E). The sodium lidar observed an SSL at 21:18 UT on 22 January 2012. The SSL was observed for 18 min, with a maximum sodium density of about 1.9 × 1010 m−3 at 93 km with a 1.1 km ...
    • Change in turbopause altitude at 52 and 70° N 

      Hall, Chris; Holmen, Silje Eriksen; Meek, Chris; Manson, Alan; Nozawa, Satonori (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-02-26)
      The turbopause is the demarcation between atmospheric mixing by turbulence (below) and molecular diffusion (above). When studying concentrations of trace species in the atmosphere, and particularly long-term change, it may be important to understand processes present, together with their temporal evolution that may be responsible for redistribution of atmospheric constituents. The general ...
    • Characteristics of Arctic tides at CANDAC-PEARL (80 degrees N, 86 degrees W) and Svalbard (78 degrees N, 16 degrees E) for 2006-2009 : radar observations and comparisons with the model CMAM-DAS 

      Manson, Alan; Meek, Chris; Xu, X.; Aso, Takehiko; Drummond, J. R.; Hall, Chris; Hocking, W. K.; Tsutsumi, Masaki; Ward, W. E. (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      Operation of a Meteor Radar (MWR) at Eureka, Ellesmere Island (80° N, 86° W) began in February 2006: this is the location of the Polar Environmental and Atmospheric Research Laboratory (PEARL), operated by the "Canadian Network for the Detection of Atmospheric Change" (CANDAC). The first 36 months of tidal wind data (82–97 km) are here combined with contemporaneous tides from the Meteor Radar (MWR) ...
    • Characteristics of Arctic winds at CANDAC-PEARL (80 degrees N, 86 degrees W) and Svalbard (78 degrees N, 16 degrees E) for 2006-2009: radar observations and comparisons with the model CMAM-DAS 

      Hall, Chris (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      Operation of a Meteor Wind Radar (MWR) at Eureka, Ellesmere Island (80° N, 86° W) began in February 2006; this is the location of the Polar Environmental and Atmospheric Research Laboratory (PEARL), operated by the "Canadian Network for the Detection of Atmospheric Change" (CANDAC). The first 36 months of wind data (82–97 km) are here combined with contemporaneous winds from the Meteor Wind Radar ...
    • Climatic trends in E-region critical frequency and virtual height above Tromsø (70 degrees N, 10 degrees E) 

      Cannon, P. S.; Hall, Chris; Brekke, Asgeir (Journal article; Tidsskriftartikkel; Peer reviewed, 2007-11-29)
      We have examined the long time series of observations of E-region virtual height (1948–2006) and critical frequency (1935-2006) hitherto made by the Tromsø ionosonde at 70 degrees N, 19 degrees E. Combining a simplistic trend analysis with a rigorous treatment of errors we identify a negative trend in critical frequency. While a similar analysis of the virtual height h'E also suggests a negative ...
    • Complexity signatures for short timescales in the atmosphere above Adventdalen, Svalbard 

      Hall, Christopher (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-01-30)
    • Det historiske nordlys 

      Brekke, Asgeir; Egeland, Alf (Journal article; Tidsskriftartikkel, 1980)
      Nordlyset har vært omgitt av både mystikk og beundring. Det har inspirert kunstnere til betagende kunstverk og skremt andre til fortvilelse. Det er umulig å fastslå når den første beskrivelsen av nordlys har funnet sted. I det følgende kapitlet skal vi gå historiens vei og presentere noen inntrykk av de tidligste forestillingene om fenomenet, slike som en kan finne spør av i den muntlige tradisjon, ...
    • Determining the boundaries of the auroral oval from CHAMP field-aligned current signatures - Part 1 

      Xiong, Chao; Lühr, Hermann; Wang, Hui; Johnsen, Magnar Gullikstad (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
    • 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 (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-17)
      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 the radar observations show cusp-like characteristics. The ionospheric, interplanetary magnetic field and solar wind conditions favor dayside magnetic reconnection as the dominant ...
    • Internasjonale forpliktelser 

      Brekke, Asgeir (Journal article; Tidsskriftartikkel, 1980)
      I forbindelse med at Nordlysobservatoriet har eksistert i 50 år kan det være på sin plass å spørre om det fortsatt er behov for virksomheten. Svaret er at observatoriet fyller en viktig oppgave i internasjonal forskning.
    • Isolated lower mesospheric echoes seen by medium frequency radar at 70º N, 19º E 

      Manson, A.H.; Hall, Chris; Meek, C.E.; Nozawa, S. (Journal article; Peer reviewed; Tidsskriftartikkel, 2006-11-23)
      We have noted sporadic instances of strong isolated reflections of medium frequency (MF) radar waves from the mesosphere from as low as 50 km altitude and have devised a set of criteria for isolating these apparently anomalous echoes from those normally occurring from progressive partial reflections in the D-region. The object of this study is to map the occurrences of such echoes facilitating ...
    • Maximilian Hell's geomagnetic observations in Norway 1769 

      Aspaas, Per Pippin; Hansen, Truls Lynne (Research report; Forskningsrapport, 2005)
      In the years 1768-1770 an expedition lead by the Austrian/Hungarian astronomer and Jesuit Father Maximilian Hell travelled to Vardø in the northernmost part of Norway. The main objective of the expedition was to observe the transit of Venus in June 1769. However, scientific investigations in several other fields were also performed, among them observations of the magnetic declination. From the ...
    • Mesospheric turbulence during PMWE-conducive conditions 

      Hall, Chris; Manson, Alan; Meek, Chris; Nozawa, Satonori (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)