Now showing items 867-886 of 1261

    • Plasma line studies in relation to Naturally Enhanced Ion Acoustic Lines (NEIALs) 

      Knutsen, Joachim Sveia (Master thesis; Mastergradsoppgave, 2008-06-02)
      New to the ESR common programmes is the inclusion of plasma lines along with the standard ion power density spectrum. Using data from the IPY common programme, a programme that has been run all through the International Polar Year, we have gone through large amounts of analysed data trying to find periods in time that fulfils the known criteria for finding Naturally Enhanced Ion Acoustic Lines ...
    • Plasma-neutral gas interactions in various space environments: Assessment beyond simplified approximations as a Voyage 2050 theme 

      Yamauchi, Masatoshi; De Keyser, Johan; Parks, George; Oyama, Shin-ichiro; Wurz, Peter; Abe, Takumi; Beth, Arnaud; Daglis, Ioannis A.; Dandouras, Iannis; Dunlop, Malcolm; Henri, Pierre; Ivchenko, Nickolay; Kallio, Esa; Kucharek, Harald; Liu, Yong C.-M.; Mann, Ingrid; Marghitu, Octav; Nicolaou, Georgios; Rong, Zhaojin; Sakanoi, Takeshi; Saur, Joachim; Shimoyama, Manabu; Taguchi, Satoshi; Tian, Feng; Tsuda, Takuo; Tsurutani, Bruce; Turner, Drew; Ulich, Thomas; Yau, Andrew; Yoshikawa, Ichiro (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-26)
      In the White Paper, submitted in response to the European Space Agency (ESA) Voyage 2050 Call, we present the importance of advancing our knowledge of plasma-neutral gas interactions, and of deepening our understanding of the partially ionized environments that are ubiquitous in the upper atmospheres of planets and moons, and elsewhere in space. In future space missions, the above task ...
    • Platelet ice under Arctic pack ice in winter 

      Katlein, Christian; Mohrholz, Volker; Sheikin, Igor; Itkin, Polona; Divine, Dmitry; Stroeve, Julienne C.; Jutila, Arttu; Krampe, Daniela; Shimanchuk, Egor; Raphael, Ian; Rabe, Benjamin; Kuznetsov, Ivan; Mallet, Maria; Liu, Hailong; Hoppmann, Mario; Fang, Ying‐Chih; Dumitrascu, Adela; Arndt, Stefanie; Anhaus, Philipp; Nicolaus, Marcel; Matero, Ilkka; Oggier, Marc; Eicken, Hajo; Haas, Christian (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-17)
      The formation of platelet ice is well known to occur under Antarctic sea ice, where subice platelet layers form from supercooled ice shelf water. In the Arctic, however, platelet ice formation has not been extensively observed, and its formation and morphology currently remain enigmatic. Here, we present the first comprehensive, long‐term in situ observations of a decimeter thick subice platelet ...
    • Polar low trajectories in the Nordic Seas 1999-2013: a statistical analysis using kernel density methods 

      Kvammen, Ylva Kirsten (Master thesis; Mastergradsoppgave, 2014-06-02)
      Polar lows are mesoscale cyclones of high intensity, frequently occurring in the Nordic Seas during the winter season. They usually form in baroclinic zones, for instance in regions near ice edges, and they are often maintained by organized convection. Polar lows are characterized by severe weather conditions like heavy snowfall, strong winds, icing and large sea waves. In addition to forecasting ...
    • Polar Lows - Moist Baroclinic Cyclones in Four Different Vertical Wind Shear Environments 

      Stoll, Patrick; Spengler, Thomas; Terpstra, Annick; Graversen, Rune (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-15)
      Polar lows are intense mesoscale cyclones that develop in polar marine air masses. Motivated by the large variety of their proposed intensification mechanisms, cloud structure, and ambient sub-synoptic environment, we use self-organising maps to classify polar lows. The method is applied to 370 polar lows in the north-eastern Atlantic, which were obtained by matching mesoscale cyclones from ...
    • Polar Mesospheric Winter Echoes - an analysis of selected cases 

      Ettestad, Kristine (Mastergradsoppgave; Master thesis, 2022-05-31)
      Polar Mesospheric Winter Echoes (PMWE) are strong coherent radar echoes, from the upper mesosphere at 55-85 km that are observed typically from end of August until beginning of May. Some models to explain PMWE formation suggest that they form because of turbulence in the atmosphere. Other models suggest that the PMWEs form like summer polar mesospheric echoes (PMSE) where charged dust particles ...
    • Polarimetric Guided Nonlocal Means Covariance Matrix Estimation for Defoliation Mapping 

      Agersborg, Jørgen Andreas; Anfinsen, Stian Normann; Jepsen, Jane Uhd (Conference object; Konferansebidrag, 2020)
      In this study we investigate the potential for using synthetic aperture radar (SAR) data to provide high resolution defoliation and regrowth mapping of trees in the tundra-forest ecotone. Using aerial photographs, four areas with live forest and four areas with dead trees were identified. Quad-polarimetric SAR data from RADARSAT-2 was collected from the same area, and the complex multilook polarimetric ...
    • Polarimetric SAR Change Detection with the Complex Hotelling-Lawley Trace Statistic 

      Akbari, Vahid; Anfinsen, Stian Normann; Doulgeris, Anthony Paul; Eltoft, Torbjørn; Moser, Gabriele; Serpico, Sebastian Bruno (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-03-15)
      In this paper, we propose a new test statistic for unsupervised change detection in polarimetric radar images. We work with multilook complex covariance matrix data, whose underlying model is assumed to be the scaled complex Wishart distribution. We use the complex-kind Hotelling-Lawley trace statistic for measuring the similarity of two covariance matrices. The distribution of the Hotelling-Lawley ...
    • Poleward energy transport: is the standard definition physically relevant at all time scales? 

      Liang, Minyi; Czaja, Arnaud; Graversen, Rune; Tailleux, Remi (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-17)
      Poleward energy transport in the atmosphere and oceans constitutes an important branch of the global energy budget, and its role in the climate system has been the subject of many studies. In the atmosphere, the transport is affected by “eddies” and large scale meridional cells, both with zero net mass transport across latitude circles, but also partly by processes associated with a net transport ...
    • A Possible Explanation of Interhemispheric Asymmetry of Equatorial Plasma Bubbles in Airglow Images 

      Hickey, Dustin A.; Sau, Sukanta; Narayanan, Viswanathan Lakshmi; Gurubaran, S. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-28)
      Equatorial plasma bubbles resulting from equatorial spread urn:x-wiley:jgra:media:jgra55597:jgra55597-math-0002 are well known to be aligned along the Earth's geomagnetic fields. During the geomagnetic storm on 17 March 2015, all‐sky airglow observations from Tirunelveli (8.7°N, 77.8°E, 1.7°N dip latitude) showed an apparent interhemispheric asymmetry in the tilt of the equatorial plasma bubbles. ...
    • Possible gas hydrates on the Bjarmeland Platform; seismic expression and stability modelling 

      Løvaas, John Sverre (Master thesis; Mastergradsoppgave, 2016-05-24)
      Seismic evidence of shallow gas anomalies are prominent at Ververis Dome structure and Hoop Fault Complex in Bjarmeland Platform. Ubiquitous high amplitude anomalies at the same depth as these shallow gas anomalies infer a possible relation to gas hydrates. A wide range of fluid flow structures within the two study areas have previously been discovered and reported, and may possibly feed the base ...
    • Power law spectra and intermittent fluctuations due to uncorrelated Lorentzian pulses 

      Garcia, Odd Erik; Theodorsen, Audun (Peer reviewed; Journal article; Tidsskriftsartikkel, 2017-02)
      A stochastic model for intermittent fluctuations due to a super-position of uncorrelated Lorentzian pulses is presented. For a constant pulse duration, this is shown to result in an exponential power spectral density for the stationary process. A random distribution of pulse durations modifies the frequency spectrum, and several examples are shown to result in power law spectra. The distribution of ...
    • Power potential of Rystraumen, Norway 

      Solbakken, Kine (Master thesis; Mastergradsoppgave, 2014-03-14)
      The maximum power potential of the tidal current Rystraumen close to Troms , Norway, is assessed both theoretically and from a depth-integrated numerical model (FVCOM). For the theoretical estimate of the maximum power potential, the topography is simplified to the situation in which the channel connects a large basin, unaffected by the energy extraction, to a closed bay. A set of governing equations ...
    • Power-law scaling of uncorrelated plasma bursts 

      Theodorsen, Audun; Garcia, Odd Erik; Rypdal, Martin wibe (Conference object; Konferansebidrag, 2019-07)
    • Preconditioning of Summer Melt Ponds From Winter Sea Ice Surface Temperature 

      Thielke, Linda; Fuchs, Niels; Spreen, Gunnar; Tremblay, Bruno; Birnbaum, Gerit; Huntemann, Marcus; Hutter, Nils; Itkin, Polona; Jutila, Arttu; Webster, Melinda A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-22)
      Comparing helicopter-borne surface temperature maps in winter and optical orthomosaics in summer from the year-long Multidisciplinary drifting Observatory for the Study of Arctic Climate expedition, we find a strong geometric correlation between warm anomalies in winter and melt pond location the following summer. Warm anomalies are associated with thinner snow and ice, that is, surface depression ...
    • Predicting Energy Demand in Semi-Remote Arctic Locations 

      Foldvik Eikeland, Odin; Bianchi, Filippo Maria; Chiesa, Matteo; Apostoleris, Harry; Hansen, Morten; Chiou, Yu-Cheng (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-03)
      Forecasting energy demand within a distribution network is essential for developing strategies to manage and optimize available energy resources and the associated infrastructure. In this study, we consider remote communities in the Arctic located at the end of the radial distribution network without alternative energy supply. Therefore, it is crucial to develop an accurate forecasting model to ...
    • Predicting Regions of Local Recurrence in Glioblastomas Using Voxel-Based Radiomic Features of Multiparametric Postoperative MRI 

      Cepeda, Santiago; Luppino, Luigi Tommaso; Pérez-Núñez, Angel; Solheim, Ole Skeidsvoll; García-García, Sergio; Velasco-Casares, María; Karlberg, Anna Maria; Eikenes, Live; Sarabia, Rosario; Arrese, Ignacio; Zamora, Tomás; Gonzalez, Pedro; Jiménez-Roldán, Luis; Kuttner, Samuel (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-22)
      The globally accepted surgical strategy in glioblastomas is removing the enhancing tumor. However, the peritumoral region harbors infiltration areas responsible for future tumor recurrence. This study aimed to evaluate a predictive model that identifies areas of future recurrence using a voxel-based radiomics analysis of magnetic resonance imaging (MRI) data. This multi-institutional study included ...
    • Predicting the Auroral Oval Boundaries by Means of Polar Operational Environmental Satellite Particle Precipitation Data 

      Breedveld, Mikkel Jelle (Master thesis; Mastergradsoppgave, 2020-06-29)
      New empirical Kp-based models for the equatorward and poleward boundaries of the auroral oval in the Northern and Southern Hemispheres were developed, with the purpose of reviewing the auroral ovals predicted by well-established Feldstein auroral oval model. The new models were derived from particle and energy flux measurements from six low-altitude (800-900 km) POES/MetOp satellites. The equatorward ...
    • Predicting the suitability of lateritic soil type for low cost sustainable housing with image recognition and machine learning techniques 

      Olukan, Tuza Adeyemi; Chiou, Yu-Cheng; Chiu, Cheng-Hsiang; Lai, Chia-Yun; Santos Hernandez, Sergio; Chiesa, Matteo (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-10)
      From a sustainability point of view, laterites-compressed earth bricks (LCEB) are a promising substitute for building structures in place of the conventional concrete masonry units. On the other hand, techniques for identifying and classifying laterites soil for compressed earth bricks (CEB) production are still relying on direct human expertise or ‘experts’. Human experts exploit direct visual ...
    • Preliminary Assessment of Remote Wind Sites 

      Bilal, Muhammad; Araya, Guillermo; Birkelund, Yngve (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-08)
      Wind energy is becoming a reliable and affordable source of clean energy and is rapidly expanding to remote places around the world. A crucial input for wind farming prospect is the assessment of potential wind sites. Sites, especially remotely located, often do not have a wind resource map and thus lack credible historical records of wind resources. Measurement campaigns to map these sites are ...