Now showing items 21-40 of 64

    • Long-range memory in Earth surface temperatures: spatial scale dependence and land-sea differences 

      Fredriksen, Hege-Beate (Master thesis; Mastergradsoppgave, 2013-05-15)
      The use of long-range memory models as a description of the noise in Earth surface temperatures has increased the recent years, and as a measure of the persistence for such time series we have the Hurst exponent. It is known that sea surface temperatures are more persistent than land temperatures, and that global temperatures are more persistent than local temperatures. We also know that the persistence ...
    • Temperature sensitivity of waveguide Mach-Zehnder interferometer 

      Sokolov, Viktor (Master thesis; Mastergradsoppgave, 2013-05-31)
      This thesis is part of a project that aims to develop a sensor for the detection of methane in the air and in water based on a waveguide Mach-Zehnder interferometer. The main application of this sensor is monitoring the environment and the ability to detect a leakage of methane. The development of a sensor includes analysis of operational conditions. In this project one of the greatest concerns is ...
    • Statistical analysis of fluctuations in the Alcator C-Mod scrape-off layer 

      Fritzner, Sindre Markus (Master thesis; Mastergradsoppgave, 2013-06-30)
      Experimental data from Alcator C-Mod have been used to analyze large density events occurring at the edge of fusion reactors. The data acquisition methods used are gas puff imaging and Langmuir probes. The data consist of long time series sampled at high frequency, excellent for statistical analysis. Large density events have been analyzed where blobs are found to be consistent with high skewness ...
    • Reduced models for geophysical fluid dynamics 

      Sortland, Daniel Selnes (Master thesis; Mastergradsoppgave, 2013-07-16)
      This thesis present a self-consistent derivation of reduced fluid models for geophysical dynamics confined to the midlatitude region. The reduced model will be derived by use of a regular perturbation method, that gives the same result as the classical models, such as the barotropic and baroclinic quasi-gestrophic potential vorticity model. It will be shown that such a rigorous treatment self-consistently ...
    • On the relation between type-II ion outflow and naturally enhanced ion acoustic lines in the polar ionosphere 

      Di Loreto, Massimo (Master thesis; Mastergradsoppgave, 2013-11-15)
      In this work we investigated the relation between type-II ion outflows and NEIALs. Currently, several ion outflows acceleration mechanisms and NEIALs generation theories have been proposed. In the first part of this thesis we review the most important works regarding these two processes. In the second part we present the results of our analysis, together with some unexpected events which were not ...
    • Type-I ion outflow from the high latitude ionosphere 

      Argese, Chiara (Master thesis; Mastergradsoppgave, 2013-11-15)
      The aim of this thesis is to study type-I ion outflows in the high latitude ionosphere. Type-I ion outflows are characterized by strong perpendicular electric fields, enhanced and anisotropic ion temperatures and low electron densities below 300 km, indicating small amounts of hard particle precipitation. We scanned data from the EISCAT Madrigal database over a period of 10 years (January 2000 - ...
    • Simulating and characterizing carbon based solar thermal absorbers 

      Jain, Amitap (Master thesis; Mastergradsoppgave, 2014-05-16)
      The main objective of this project is to determine and characterize the optical and structural properties of carbon nanotube (CNT) coated aluminum substrates to facilitate better understanding regarding their suitability for solar absorption. In this way, it may be possible to utilize this material to produce improved and more efficient spectrally selective solar thermal absorbers in solar thermal ...
    • Quantifying influence of local air pollution on measurements in Ny-Ålesund and at the Zeppelin station 

      Dekhtyareva, Alena (Master thesis; Mastergradsoppgave, 2014-06-02)
      In order to keep the scientific significance of the Ny-Ålesund station on Svalbard as the key place for the monitoring of background air it is needed to assess the influence from local human activities on the air quality. Whether research and tourist activity continues to grow or restrictions to be implied the change of impact may affect air chemistry data quality. Therefore the identification of ...
    • Stochastic modelling of intermittent scrape-off layer plasma fluctuations 

      Theodorsen, Audun (Master thesis; Mastergradsoppgave, 2015-05-15)
      In the tokamak scrape-off layer, radial motion of blob-like structures is the dominant mechanism for transport of particles and heat. Fixed point probe measurements in the Tokamak à Configuration Variable scrape-off layer reveal highly intermittent fluctuations in the ion saturation current. These measurements are well described by a shot noise process with exponential pulse shapes, exponentially ...
    • The impact of Arctic late summer sea ice variability on mid-latitude autumn and winter weather. 

      Stoll, Patrick (Master thesis; Mastergradsoppgave, 2015-11-18)
      The influence of Arctic summer sea ice area on autumn and winter climate in the extra-tropic Northern hemisphere is investigated. During the last decades, the Arctic has warmed more than twice the global average rate, a phenomenon called the Arctic Amplification (AA). AA involves a remarkable decrease of the Arctic sea ice cover and a decrease of the latitudinal temperature gradient. Both are supposed ...
    • Sensitivity to pressure and methane of a cryptophane-A doped polymer 

      Ingvaldsen, Martin (Master thesis; Mastergradsoppgave, 2015-12-15)
      The principle focus of this thesis is the characterization of an on-chip methane sensor based on a waveguide interferometer. It incorporates cryptophane-A molecules in the waveguide cladding to enhance sensitivity and selectivity towards methane. First, the sensor was characterized for sensitivities to ambient conditions, in particular its temperature and pressure sensitivity. The measurement ...
    • Super-Resolution Imaging of Sub-Mitochondrial Structures using Structured Illumination Microscopy 

      Opstad, Ida Sundvor (Master thesis; Mastergradsoppgave, 2016-05-15)
      Modern science is based on observation, and its advances are limited by what is possible to observe. For centuries optical microscopy was limited by the diffraction of light, making structures closer together than half the wavelength of light unresolvable. In recent years, the new field of optical nanoscopy has emerged, enabling diffraction-limited structures to be resolved. As opposed to ...
    • Investigation of the ion composition in the topside ionosphere at solar maximum using incoherent scatter technique 

      Shulha, Maryna Oleksiivna (Master thesis; Mastergradsoppgave, 2016-05-15)
      The aim of this study was to investigate the altitudinal and diurnal variations of light ion densities in the topside ionosphere during the 23rd and 24th solar maximums. This made it possible to understand the behavior of the ion composition after extended solar minimum and compare how it differs from the preceding solar maximum. The observed variations are compared with estimates of empirical (IRI) ...
    • Investigations of ionospheric disturbances using coherent HF instrumentation 

      Reznychenko, Artem (Master thesis; Mastergradsoppgave, 2016-05-15)
      This work is based on long term monitoring the HF signal data at 9.996 MHz at mid-latitudes from the short radio-path Moscow-Kharkiv and at high-latitudes from the longer radio-path Moscow-Tromso for 2013. The HF signal transmitter is the radio station RWM in Moscow, Russia. The receiver stations are located in Tromso (Norway) and Kharkiv (Ukraine). Using intensity and the Doppler frequency shift ...
    • Numerical computations of turbulent motions in magnetized plasmas 

      Decristoforo, Gregor (Master thesis; Mastergradsoppgave, 2016-05-18)
      Intermittent fluctuations and turbulence-induced transport of magnetically confined fusion plasmas are investigated by numerical computations. A reduced fluid model describing the evolution of plasma pressure and electric drift vorticity in a two-dimensional plane perpendicular to the magnetic field is derived. A numerical simulation code implemented on graphical processing units is presented. We ...
    • Effect of permanent magnets on plasma confinement and ion beam generation in a double layer helicon plasma source 

      Varberg, Erik (Master thesis; Mastergradsoppgave, 2016-06-01)
      The work described in this thesis was carried out to investigate how additional permanent magnets (PM) could affect the confinement and ion beam generation in a plasma which expands from a helicon source. PMs added to a plasma source systems has been shown to provide an increased plasma confinement, but is not widely used. This inexpensive and cheap method of using PMs which does not require any ...
    • System upgrade and data evaluation of the AIRIS riometer 

      Larsen, Ida Marie (Master thesis; Mastergradsoppgave, 2016-06-06)
      The focus of this thesis has been to investigate how to improve the AIRIS data. This has been done by first of all giving the riometer system an overhaul, checking the wiring and receivers as well as upgrading the riometer computer harddisk. As there has been a lot of issues occurring along the way, the focus finally went to pinpointing exactly what is causing the data quality to be poor and coming ...
    • The volume distribution of artificial aurora induced by HF radio waves in the ionosphere 

      Kvammen, Andreas (Master thesis; Mastergradsoppgave, 2016-08-15)
      This thesis presents three-dimensional modelling of artificial aurora in the ionospheric F layer, induced by high frequency (HF) O-mode radio waves from the EISCAT heating facility. Understanding how HF radio waves produces enhanced emission in the ionosphere has been one of the one of the major motivations for conducting heating experiments during the last decades. A key element for understanding ...
    • Laser diagnostics of the mesospheric magnetic field. Understanding remote laser magnetometry in northern Norway 

      Serrano, Alessandra (Master thesis; Mastergradsoppgave, 2017-05-15)
      This thesis outlines initial motivations and propositions for the Mesospheric Optical Magnetometry (MOM) project, using lidar equipment at ALOMAR observatory in northern Norway to initiate a novel technique for measuring Earth’s magnetic field at approximately 90 km altitude. Included is an in-depth discussion of the physical phenomena within Earth’s mesospheric sodium layer, relevant atomic physics, ...
    • Optimization of a polymer layer highly doped with Cryptophane-A for methane sensing 

      Yadav, Mukesh (Master thesis; Mastergradsoppgave, 2017-05-15)
      The main objective of this thesis is to optimize the thickness of sensitive polymer layer highly doped with Cryptophane-A for methane pre-concentration and to make the existing sensor more stable and selective towards methane. In recent years, methane detection has become a hot topic due to the strong impact of methane on the global warming and the climate change. There has also been rising ...