Now showing items 491-510 of 519

  • Stepan, J.; Trujillo Bueno, J.; Leenaarts, Jorrit; Carlsson, Mats (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    Probing the magnetism of the upper solar chromosphere requires measuring and modeling the scattering polarization produced by anisotropic radiation pumping in UV spectral lines. Here we apply PORTA ( a novel radiative ...
  • Dahle, Håkon; Gladders, M. D.; Sharon, K.; Bayliss, M. B.; Rigby, J. R. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    We report fi rst results from an ongoing monitoring campaign to measure time delays between the six images of the quasar SDSS J2222 + 2745, gravitationally lensed by a galaxy cluster. The time delay between A and B, the ...
  • Dyrland, Karianne (Master thesis / Masteroppgave, 2019)
  • Martinez-Sykora, Juan; De Pontieu, Bart Walter; Hansteen, Viggo; Gudiksen, Boris Vilhelm (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
    The properties of nonstatistical equilibrium ionization of silicon and oxygen ions are analyzed in this work. We focus on five solar targets (quiet Sun; coronal hole; plage; quiescent active region, AR; and flaring AR) as ...
  • Mouland, Maria (Master thesis / Masteroppgave, 2009)
    I have investigated the total energy of Friedmann-Robertson-Walker universes. This is an interesting issue, because if the energy of the universe turns out not to be conserved, it will be in conflict with our common ...
  • Eide, Marius Berge (Master thesis / Masteroppgave, 2015)
  • Biswas, T.; Gerwick, E.; Koivisto, Tomi Sebastian; Mazumdar, A. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)
    We present the most general covariant ghost-free gravitational action in a Minkowski vacuum. Apart from the much studied f(R) models, this includes a large class of nonlocal actions with improved UV behavior, which ...
  • Christensen, Charlotte R.; Davé, Romeel; Brooks, Alyson M.; Quinn, Thomas; Shen, Sijing (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    We analyze the metal accumulation in dwarf and spiral galaxies by following the history of metal enrichment and outflows in a suite of 20 high-resolution simulated galaxies. These simulations agree with the observed stellar ...
  • Groeneboom, Nicolaas Ervik (Master thesis / Masteroppgave, 2007)
  • Jafarzadeh, Shahin; Solanki, S. K.; Gafeira, Ricardo; van Noort, M.; Barthol, P.; Blanco Rodriguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L; Hirzberger, J.; Knölker, M.; Orozco Suarez, D.; Riethmüller, T. L.; Schmidt, W. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
    We present observations of transverse oscillations in slender Ca ii H fibrils (SCFs) in the lower solar chromosphere. We use a 1 hr long time series of high- (spatial and temporal-) resolution seeing-free observations in ...
  • Antolin, Patrick; Schmit, D.; Pereira, Tiago Mendes Domingos; De Pontieu, Bart Walter; De Moortel, I. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    In addition to their jet-like dynamic behavior, spicules usually exhibit strong transverse speeds, multi-stranded structure, and heating from chromospheric to transition region temperatures. In this work we first analyze ...
  • Martinez-Sykora, Juan; De Pontieu, Bart Walter; Carlsson, Mats; Hansteen, Viggo; Nobrega-Siverio, Daniel; Gudiksen, Boris Vilhelm (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
    We investigate the effects of interactions between ions and neutrals on the chromosphere and overlying corona using 2.5D radiative MHD simulations with the Bifrost code. We have extended the code capabilities implementing ...
  • Allred, Joel C.; Kowalski, Adam F.; Carlsson, Mats (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    We present a unified computational framework that can be used to describe impulsive flares on the Sun and on dMe stars. The models assume that the flare impulsive phase is caused by a beam of charged particles that is ...
  • Brax, P; Davis, A.-C.; Li, Baojiu; Winther, Hans Arnold (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)
    We consider modified gravity models driven by a scalar field whose effects are screened in high density regions due to the presence of nonlinearities in its interaction potential and/or its coupling to matter. Our approach ...
  • Salzano, Vincenzo; Mota, David; Capoziello, S.; Napolitano, N. R. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
    Aims: We investigated the gravitational effects of a scalar field within scalar-tensor gravity as an alternative to dark matter. Motivated by chameleon, symmetron, and f(R)-gravity models, we studied a phenomenological ...
  • Gronke, Max Balthasar; Mota, David; Winther, Hans Arnold (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    Modified gravity models require a screening mechanism to be able to evade the stringent constraints from local gravity experiments and, at the same time, give rise to observable astrophysical and cosmological signatures. ...
  • Mason, Charlotte A.; Treu, Tommaso; Dijkstra, Mark; Mesinger, Andrei; Trenti, Michele; Pentericci, Laura; De Barros, Stephane; Vanzella, Eros (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    We present a new flexible Bayesian framework for directly inferring the fraction of neutral hydrogen in the intergalactic medium (IGM) during the Epoch of Reionization (EoR, z ~ 6–10) from detections and non-detections of ...
  • Eide, Marius Berge; Gronke, Max Balthasar; Dijkstra, Mark; Hayes, Matthew (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    Lyα is a powerful astrophysical probe. Not only is it ubiquitous at high redshifts, it is also a resonant line, making Lyα photons scatter. This scattering process depends on the physical conditions of the gas through which ...
  • Scullion, Eamon; Rouppe, Van Der Voort Luc; Wedemeyer-Böhm, Sven; Antolin, Patrick (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
    New and advanced space-based observing facilities continue to lower the resolution limit and detect solar coronal loops in greater detail. We continue to discover even finer substructures within coronal loop cross-sections, ...
  • Ingebrigtsen, Tony Asle (Master thesis / Masteroppgave, 2010)
    The statistical analysis of the Cosmic Microwave Background radiation to make estimates of the Power Spectrum is a comutationally heavy operation, involving large covariance matrices. In this thesis I explore the possibility ...