• Atmospheric tomography using the Nordic Meteor Radar Cluster and Chilean Observation Network de Meteor Radars: Network details and 3D-Var retrieval 

      Stober, Gunter; Kozlovsky, A.; Liu, Alan; Qiao, Zishun; Tsutsumi, Masaki; Hall, Chris; Nozawa, Satonori; Lester, Mark; Belova, Evgenia; Kero, Johan; Espy, Patrick Joseph; Hibbins, Robert E.; Mitchell, N. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-08)
      Ground-based remote sensing of atmospheric parameters is often limited to single station observations by vertical profiles at a certain geographic location. This is a limiting factor for investigating gravity wave dynamics as the spatial information is often missing, e.g., horizontal wavelength, propagation direction or intrinsic frequency. In this study, we present a new retrieval algorithm for ...
    • An automated auroral detection system using deep learning: real-time operation in Tromsø, Norway 

      Nanjo, Sota; Nozawa, Satonori; Yamamoto, Masaki; Kawabata, Tetsuya; Johnsen, Magnar Gullikstad; Tsuda, Takuo T.; Hosokawa, Keisuke (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-31)
      The activity of citizen scientists who capture images of aurora borealis using digital cameras has recently been contributing to research regarding space physics by professional scientists. Auroral images captured using digital cameras not only fascinate us, but may also provide information about the energy of precipitating auroral electrons from space; this ability makes the use of digital cameras ...
    • 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)
    • 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 ...
    • Evaluation of a method to derive ionospheric conductivities using two auroral emissions (428 and 630 nm) measured with a photometer at Tromsø (69.6°N) 

      Adachi, K; Nozawa, Satonori; Ogawa, Y; Brekke, Asgeir; Hall, Chris; Fujii, Ryochi (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-07-03)
      This paper mainly aims at evaluating capabilities of derivation of ionospheric conductivities using two principal auroral emissions (427.8 and 630 nm). We have evaluated a photometric method of derivation of ionospheric conductivities based on simultaneous observations of a photometer (feld of view = ~1.2°), a digital camera, and the EISCAT UHF radar (feld of view = ~0.7°) operated at Tromsø, ...
    • Formation of an additional density peak in the bottom side of the sodium layer associated with the passage of multiple mesospheric frontal systems 

      Narayanan, Viswanathan Lakshmi; Nozawa, Satonori; Oyama, Shin-Ichiro; Mann, Ingrid; Shiokawa, Kazuo; Otsuka, Yuichi; Saito, Norihito; Wada, Satoshi; Kawahara, Takuya D.; Takahashi, Toru (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-18)
      We present a detailed investigation of the formation of an additional sodium density peak at altitudes of 79–85 km below the main peak of the sodium layer based on sodium lidar and airglow imager measurements made at Ramfjordmoen near Tromsø, Norway, on the night of 19 December 2014. The airglow imager observations of OH emissions revealed four passing frontal systems that resembled mesospheric ...
    • Identifying gravity waves launched by the Hunga Tonga-Hunga Ha′apai volcanic eruption in mesosphere/lower-Thermosphere winds derived from CONDOR and the Nordic Meteor Radar Cluster 

      Stober, Gunter; Liu, Alan; Kozlovsky, Alexander; Qiao, Zishun; Krochin, Witali; Shi, Guochun; Kero, Johan; Tsutsumi, Masaki; Gulbrandsen, Njål; Nozawa, Satonori; Lester, Mark; Baumgarten, Kathrin; Belova, Evgenia; Mitchell, Nicholas (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-18)
      The Hunga Tonga–Hunga Ha'apai volcano eruption was a unique event that caused many atmospheric phenomena around the globe. In this study, we investigate the atmospheric gravity waves in the mesosphere/lowerthermosphere (MLT) launched by the volcanic explosion in the Pacific, leveraging multistatic meteor radar observations from the Chilean Observation Network De Meteor Radars (CONDOR) and the ...
    • Inferring neutral winds in the ionospheric transition region from atmospheric-gravity-wave traveling-ionospheric-disturbance (AGW-TID) observations with the EISCAT VHF radar and the Nordic Meteor Radar Cluster 

      Günzkofer, Florian; Pokhotelov, Dimitry; Stober, Gunter; Mann, Ingrid Brigitte; Vadas, Sharon L.; Becker, Erich; Tjulin, Anders; Kozlovsky, Alexander; Tsutsumi, Masaki; Gulbrandsen, Njål; Nozawa, Satonori; Lester, Mark; Belova, Evgenia; Kero, Johan; Mitchell, Nicholas J.; Borries, Claudia (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-18)
      Atmospheric gravity waves and traveling ionospheric disturbances can be observed in the neutral atmosphere and the ionosphere at a wide range of spatial and temporal scales. Especially at medium scales, these oscillations are often not resolved in general circulation models and are parameterized. We show that ionospheric disturbances forced by upward-propagating atmospheric gravity waves can be ...
    • Mesospheric turbulence during PMWE-conducive conditions 

      Hall, Chris; Manson, Alan; Meek, Chris; Nozawa, Satonori (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)
    • Meteor radar vertical wind observation biases and mathematical debiasing strategies including the 3DVAR+DIV algorithm 

      Stober, Gunter; Liu, Alan; Kozlovsky, Alexander; Qiao, Zishun; Kuchar, Ales; Jacobi, Christoph; Meek, Chris; Janches, Diego; Liu, Guiping; Tsutsumi, Masaki; Gulbrandsen, Njål; Nozawa, Satonori; Lester, Mark; Belova, Evgenia; Kero, Johan; Mitchell, Nicholas (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-13)
      Meteor radars have become widely used instruments to study atmospheric dynamics, particularly in the 70 to 110 km altitude region. These systems have been proven to provide reliable and continuous measurements of horizontal winds in the mesosphere and lower thermosphere. Recently, there have been many attempts to utilize specular and/or transverse scatter meteor measurements to estimate vertical ...
    • A new five-wavelength photometer operated in Tromsø (69.6°N, 19.2°E) 

      Nozawa, Satonori; Kawabata, Tetsuya; Hosokawa, Keisuke; Ogawa, Yasunobu; Tsuda, Takuo; Mizuno, Akira; Fujii, Ryoichi; Hall, Chris (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-11)
      A new fve-wavelength photometer was developed and installed at the EISCAT Tromsø site (69.6°N, 19.2°E) in January 2017. The photometer consists of two units: an optical unit and a control unit together with a PC. The photometer is capable of simultaneously observing auroral emissions with fve wavelengths. A uniqueness of the present system is its capability of precise pointing, which enables ...
    • Special issue “Recent Advances in MST and EISCAT/Ionospheric Studies – Special Issue of the Joint MST15 and EISCAT18 Meetings, May 2017” 

      Yamamoto, Mamoru; Hocking, Wayne; Nozawa, Satonori; Vierinen, Juha; Liu, Huixin; Nishitani, Nozomu (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-09-18)
      The Fifteenth Workshop on Technical and Scientific Aspects of MST Radar (MST15) and the Eighteenth EISCAT Symposium (EISCAT18) were jointly held in Tokyo, Japan, at the National Institute of Polar Research (NIPR) during May 26–31, 2017. The MST workshops have a long history of being the primary international meetings on the applications and development of mesosphere–stratosphere–troposphere (MST) ...
    • A statistical study of convective and dynamic instabilities in the polar upper mesosphere above Tromsø 

      Nozawa, Satonori; Saito, Norihito; Kawahara, Takuya D.; Wada, Satoshi; Tsuda, Takuo T.; Maeda, S; Takahashi, Toru; Fujiwara, Hitoshi; Narayanan, V L; Kawabata, T; Johnsen, Magnar Gullikstad (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-15)
      We have studied the convective (or static) and dynamic instabilities between 80 and 100 km above Tromsø (69.6° N, 19.2° E) using temperature and wind data of 6 min and 1 km resolutions primarily almost over a solar cycle obtained with the sodium lidar at Tromsø. First, we have calculated Brunt–Väisälä frequency (N) for 339 nights obtained from October 2010 to December 2019, and the Richardson ...
    • Survey of conditions for artificial aurora experiments at EISCAT Tromsø using dynasonde data 

      Tsuda, T. T.; Rietveld, Michael T; Kosch, Michael J.; Oyama, S; Hosokawa, K.; Nozawa, Satonori; Kawabata, T; Mizuno, A; Ogawa, Y (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-02-14)
      We report a brief survey on conditions for artificial aurora optical experiments in F region heating with O-mode at the EISCAT Tromsø site using dynasonde data from 2000 to 2017. The results obtained in our survey indicate the following: The possible conditions for conducting artificial aurora experiments are concentrated in twilight hours in both evening and morning, compared with late-night hours; ...