Institutt for fysikk og teknologi: Nye registreringer

Viser treff 1301-1320 av 1400

    • Crash and recovery of the potential in a toroidal plasma column, as observed by generalized conditional sampling 

      Fredriksen, Åshild; Pecseli, Hans L.; Trulsen, Jan; Fredriksen, A.A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2008)

    • Nordområdeprosjektet EISCAT 

      Brekke, Asgeir (Chronicle; Kronikk, 2011)

    • First simultaneous measurements of waves generated at the bow shock in the solar wind, the magnetosphere and on the ground 

      Clausen, L. B. N.; Behlke, Rico; Yeoman, T. K.; Fear, R. C.; Lucek, E. A.; Engebretson, M. J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)

    • Particle precipitations during NEIAL events : simultaneous ground based observations at Svalbard 

      Lorentzen, Dag Arne; Lunde, June; Gustavsson, B; Ogawa, Y; Løvhaug, U.P.; Ogawa, Yasunobu (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)
      In this paper we present Naturally Enhanced Ion Acoustic Lines (NEIALs) observed with the EISCAT Svalbard Radar (ESR). For the first time, long sequences of NEIALs are recorded, with more than 50 events within an hour, ranging from 6.4 to 140 s in duration. The events took place from ~08:45 to 10:00 UT, 22 January 2004. We combine ESR data with observations of optical aurora by a meridian scanning ...

    • Ion-dispersion and rapid electron fluctuations in the cusp : a case study 

      Buchert, Stephan C; Lunde, June; Ogawa, Yasunobu; Hirahara, Masafumi; Seki, Kanako; Ebihara, Yuusuke; Sakanoi, Takeshi; Asamura, Kazushi; Okada, Masaki; Raita, Tero; Häggström, Ingemar (Journal article; Tidsskriftartikkel; Peer reviewed, 2008)

    • Non-Gaussian Clustering of SAR images for Glacier Change Detection 

      Akbari, Vahid; Eltoft, Torbjørn; Doulgeris, Anthony Paul (Conference object; Konferansebidrag, 2010)

    • Time Series Investigation of Land Subsidence Using a Weighted Least Squares Adjustment Based on Image Mode Interferometric Data 

      Akbari, Vahid; Motagh, Mahdi; Rajabi, Mohammad Ali; Yahya, Djamour (Conference object; Konferansebidrag, 2010)
      This study presents the weighted least squares method based on Interferometric Synthetic Aperture Radar (InSAR) images to retrieve spatial-temporal evolution of land subsidence in Mashhad Valley, northeast Iran. Using the analysis of a few interferograms covering the 2003-2005 period, Motagh et al (GJI 2006) presented a preliminary analysis of the subsidence in this area. Here we extend this study ...

    • Optical trapping and propulsion of red blood cells on waveguide surfaces 

      Ahluwalia, Balpreet Singh; Mccourt, peter anthony; Huser, Thomas Rolf; Hellesø, Olav Gaute (Journal article; Tidsskriftartikkel; Peer reviewed, 2010)

    • Frequency-dependent magnetizability 

      Anelli, Marco (Master thesis; Mastergradsoppgave, 2010-11-15)
      This work discusses the theory of the magnetizability. The magnetizability is a molecular property defined as the second-order perturbation of the energy in the presence of an external magnetic field. When the magnetic field is static, perturbation and multipole theories lead to an origin-independent expression for the magnetizability, whereas for a frequency-dependent magnetic field its expression ...

    • Improved hardware stability and signal amplification in a medical microwave radiometer 

      Tobiassen, Alexander (Master thesis; Mastergradsoppgave, 2010-10-27)
      Breast cancer is one of the most frequent types of cancer in the female population today. Modern diagnostic modalities, while proven to be helpful within large scale screening programs, are inherently limited with regards to specificity and sensitivity, and use active methods for acquisition of information. A passive and non-invasive method for detection and diagnostic purposes could therefore be a ...

    • Time and temperature control of a camera 

      Kristiansen, Anders (Master thesis; Mastergradsoppgave, 2010-07-13)
      In scientific experiments there are an increasing usage of cameras, along with other instruments, to observe parameters of physical processes. In this thesis, we will discuss how a microcontroller (ATMEL ATmega 324 PA) can be used to control the operation temperature in a camera. It will be discussed why this control of temperature can be useful for the quality of the pictures. Since this thesis is ...

    • "Intelligente" læringssystemer: Fra leken Furby til spamfiltre til miljø 

      Jenssen, Robert (Conference object; Konferansebidrag, 2010-09-02)

    • Simulations of plasma filament dynamics in toroidal geometry 

      Rønningen, Petter (Master thesis; Mastergradsoppgave, 2010-05-18)
      Interchange driven propagation of so-called "blobs" arises in basic laboratory plasmas, in the scrape-off layer of fusion plasmas and as Equatorial Spread-F (ESF) phenomena. The propagation of such blobs has been demonstrated in the VTF experiment at MIT and in earlier simulations. Experimental results show that the velocity of these blobs is inverse proportional to the neutral gas pressure. These ...

    • Numerical studies of radial filament motion in toroidally confined plasmas 

      Kube, Ralph (Master thesis; Mastergradsoppgave, 2010-05)
      Numerical studies of radial filament motions in the SOL of toroidally confined plasmas are studies. We use a two dimensional two-field model to characterize blob-like structures in the radial-poloidal domain. These structures are observed to achieve velocities in the order of the ion acoustic velocity in the SOL of tokamaks and other toroidal confinement devices. By numerical means we find a ...

    • Review and test of funnel shape geometries in solar wind acceleration 

      Trollebø, Robert (Master thesis; Mastergradsoppgave, 2009-12-15)
      The origin and heating of the solar wind is still a puzzle. We review in this study the idea that the solar wind originates in coronal funnels. We place emphasis on the fast solar wind. This study provides primarily a historic overview over the development of the idea of funnel expansion. We present examples of recent solar wind studies that investigate the funnel geometry. These studies include ...

    • On the relationship between auroral absorption, electrojet currents and plasma convection 

      Hansen, Truls Lynne; Kellerman, A. C.; Makarevich, R. A.; Honary, F. (Journal article; Tidsskriftartikkel; Peer reviewed, 2009-02-02)
      In this study, the relationship between auroral absorption, electrojet currents, and ionospheric plasma convection velocity is investigated using a series of new methods where temporal correlations are calculated and analysed for different events and MLT sectors. We employ cosmic noise absorption (CNA) observations obtained by the Imaging Riometer for Ionospheric Studies (IRIS) system in ...

    • 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 ...

    • Phenomena induced by powerful HF pumping towards magnetic zenith with a frequency near the F-region critical frequency and the third electron gyro harmonic frequency 

      Brekke, Asgeir; Blagoveshchenskaya, N. F.; Carlson, H. C.; Kornienko, V. A.; Borisova, T. D.; Rietveld, M. T.; Yeoman, T. K. (Journal article; Tidsskriftartikkel; Peer reviewed, 2009-01-08)
      Multi-instrument observational data from an experiment on 13 October 2006 at the EISCAT/HEATING facility at Tromsø, Norway are analysed. The experiment was carried out in the evening hours when the electron density in the F-region dropped, and the HF pump frequency fH was near and then above the critical frequency of the F2 layer. The distinctive feature of this experiment is that the pump frequency ...

    • Generation of the lower-thermospheric vertical wind estimated with the EISCAT KST radar at high latitudes during periods of moderate geomagnetic disturbance 

      Brekke, Asgeir; Oyama, S; Watkins, B. J.; Maeda, S.; Shinagawa, H.; Nozawa, S.; Ogawa, Y.; Lathuillere, C.; Kofman, W. (Journal article; Tidsskriftartikkel; Peer reviewed, 2008-06-11)
      Lower-thermospheric winds at high latitudes during moderately-disturbed geomagnetic conditions were studied using data obtained with the European Incoherent Scatter (EISCAT) Kiruna-Sodankylä-Tromsø (KST) ultrahigh frequency (UHF) radar system on 9–10 September 2004. The antenna-beam configuration was newly designed to minimize the estimated measurement error of the vertical neutralwind speed in the ...

    • A multiwavelet approach to the direct solution of the Poisson equation: implementation and optimization 

      Jensen, Stig Rune (Master thesis; Mastergradsoppgave, 2009-11-15)
      This work is presenting a fully numerical approach for the direct solution of the Poisson equation for the electrostatic potential given by an arbitrary charge density. Efficient solution of this equation is important in many fields of science, where the current work is dealing with nuclear and electronic potential calculations, used in the field of computational chemistry. The equation is solved ...