Browsing Institutt for teoretisk astrofysikk by Author "Hansteen, Viggo"

Now showing items 21-39 of 39

  • An interface region imaging spectrograph first view on solar spicules 
    Pereira, Tiago Mendes Domingos; De Pontieu, Bart Walter; Carlsson, Mats; Hansteen, Viggo; Tarbell, T.D.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Wulser, J. P.; Martinez-Sykora, Juan; Kleint, L.; Golub, L.; McKillop, S.; Reeves, K. K.; Saar, S.; Testa, Paola; Tian, H; Jaeggli, S.; Kankelborg, C. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
    Solar spicules have eluded modelers and observers for decades. Since the discovery of the more energetic type II, spicules have become a heated topic but their contribution to the energy balance of the low solar atmosphere ...
  • Intermittent Reconnection and Plasmoids in UV Bursts in the Low Solar Atmosphere 
    Rouppe van der Voort, Luc; De Pontieu, Bart Walter; Scharmer, G. B.; de la Cruz Rodriguez, Jaime; Martinez-Sykora, Juan; Nobrega-Siverio, Daniel; Guo, L. J.; Jafarzadeh, Shahin; Mendes Domingos Pereira, Tiago; Hansteen, Viggo; Carlsson, Mats; Vissers, Gregal Joan Maria (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
    Magnetic reconnection is thought to drive a wide variety of dynamic phenomena in the solar atmosphere. Yet, the detailed physical mechanisms driving reconnection are difficult to discern in the remote sensing observations ...
  • Internetwork Chromospheric Bright Grains Observed with IRIS and SST 
    Martinez-Sykora, Juan; Rouppe, Van Der Voort Luc; Carlsson, Mats; De Pontieu, Bart Walter; Mendes Domingos Pereira, Tiago; Boerner, P.; Hurlburt, N.; Kleint, Lucia; Lemen, J.; Tarbell, Ted D.; Title, A.; Wüelser, Jean Pierre; Hansteen, Viggo; Golub, Leon; McKillop, S.; Reeves, K. K.; Saar, S.; Testa, Paola; Tian, Hui; Jaeggli, S.; Kankelborg, C. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    The Interface Region Imaging Spectrograph (IRIS) reveals small-scale rapid brightenings in the form of bright grains all over coronal holes and the quiet Sun. These bright grains are seen with the IRIS 1330, 1400, and 2796 ...
  • Multi-component Decomposition of Astronomical Spectra by Compressed Sensing 
    Cheung, Mark C. M.; De Pontieu, Bart Walter; Martinez-Sykora, Juan; Testa, Paola; Winebarger, Amy R.; Daw, Adrian N.; Hansteen, Viggo; Antolin, Patrick; Tarbell, Theodore D.; Wüelser, Jean Pierre; Young, Peter (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2019)
    The signal measured by an astronomical spectrometer may be due to radiation from a multi-component mixture of plasmas with a range of physical properties (e.g., temperature, Doppler velocity). Confusion between multiple ...
  • NUMERICAL SIMULATIONS of CORONAL HEATING THROUGH FOOTPOINT BRAIDING 
    Hansteen, Viggo; Guerreiro, Nuno Miguel Rodrigues; De Pontieu, Bart Walter; Carlsson, Mats (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    Advanced three-dimensional (3D) radiative MHD simulations now reproduce many properties of the outer solar atmosphere. When including a domain from the convection zone into the corona, a hot chromosphere and corona are ...
  • NUMERICAL SIMULATIONS OF SPICULE ACCELERATION 
    Guerreiro, Nuno Miguel Rodrigues; Carlsson, Mats; Hansteen, Viggo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2013)
    Observations in the Hα line of hydrogen and the H and K lines of singly ionized calcium on the solar limb reveal the existence of structures with jet-like behavior, usually designated as spicules. The driving mechanism for ...
  • On the generation of solar spicules and Alfvenic waves 
    Martinez-Sykora, Juan; De Pontieu, Bart Walter; Hansteen, Viggo; Rouppe van der Voort, Luc; Carlsson, Mats; Mendes Domingos Pereira, Tiago (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2017)
    In the lower solar atmosphere, the chromosphere is permeated by jets known as spicules, in which plasma is propelled at speeds of 50 to 150 kilometers per second into the corona. The origin of the spicules is poorly ...
  • On the Origin of the Magnetic Energy in the Quiet Solar Chromosphere 
    Martinez-Sykora, Juan; Hansteen, Viggo; Gudiksen, Boris Vilhelm; Carlsson, Mats; De Pontieu, Bart Walter; Gošić, Milan (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2019)
    The presence of magnetic field is crucial in the transport of energy through the solar atmosphere. Recent ground-based and space-borne observations of the quiet Sun have revealed that magnetic field accumulates at photospheric ...
  • A publicly available simulation of an enhanced network region of the Sun 
    Carlsson, Mats; Hansteen, Viggo; Gudiksen, Boris Vilhelm; Leenaarts, Jorrit; De Pontieu, Bart Walter (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
    Context. The solar chromosphere is the interface between the solar surface and the solar corona. Modelling of this region is difficult because it represents the transition from optically thick to thin radiation escape, ...
  • Self-consistent 3D radiative magnetohydrodynamic simulations of coronal rain formation and evolution 
    Kohutova, Petra; Antolin, Patrick; Popovas, Andrius; Szydlarski, Mikolaj Marcin; Hansteen, Viggo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    Context. Coronal rain consists of cool and dense plasma condensations formed in coronal loops as a result of thermal instability. Aims. Previous numerical simulations of thermal instability and coronal rain formation have ...
  • Small-scale Heating Events in the Solar Atmosphere. I. Identification, Selection, and Implications for Coronal Heating 
    Guerreiro, Nuno Miguel Rodrigues; Haberreiter, M.; Hansteen, Viggo; Schmutz, W (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    We present a comprehensive method to analyze small-scale heating events in detail in a 3D magnetohydrodynamics simulation for quiet-Sun conditions. The method determines the number, volume, and some general geometric ...
  • Small-scale heating events in the solar atmosphere: II. Lifetime, total energy, and magnetic properties 
    Guerreiro, Nuno Miguel Rodrigues; Haberreiter, M.; Hansteen, Viggo; Schmutz, W. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
    Context. Small-scale heating events (SSHEs) are believed to play a fundamental role in understanding the process responsible for heating of the solar corona, the pervading redshifts in the transition region, and the ...
  • Small-scale Magnetic Flux Emergence in the Quiet Sun 
    Moreno-Insertis, F.; Martinez-Sykora, Juan; Hansteen, Viggo; Munoz, D. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    Small bipolar magnetic features are observed to appear in the interior of individual granules in the quiet Sun, signaling the emergence of tiny magnetic loops from the solar interior. We study the origin of those features ...
  • Synthesized spectra of optically thin emission lines produced by the Bifrost stellar atmosphere code, including nonequilibrium ionization effects: A study of the intensity, nonthermal line widths, and Doppler shifts 
    Olluri, Kosovare; Gudiksen, Boris Vilhelm; Hansteen, Viggo; De Pontieu, Bart Walter (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    In recent years realistic 3D numerical models of the solar atmosphere have become available. The models attempt to recreate the solar atmosphere and mimic observations in the best way, in order to make it possible to couple ...
  • The Multi-slit Approach to Coronal Spectroscopy with the Multi-slit Solar Explorer (MUSE) 
    De Pontieu, Bart Walter; Martinez-Sykora, Juan; Testa, Paola; Winebarger, Amy R.; Daw, Adrian N.; Hansteen, Viggo; Cheung, Mark C. M.; Antolin, Patrick (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2019)
    The Multi-slit Solar Explorer (MUSE) is a proposed mission aimed at understanding the physical mechanisms driving the heating of the solar corona and the eruptions that are at the foundation of space weather. MUSE contains ...
  • The Solar Orbiter SPICE instrument: An extreme UV imaging spectrometer 
    Anderson, Mark; Appourchaux, T.; Auchère, Frédéric; Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini, Karine; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.; Caldwell, M.; Caminade, S.; Carlsson, Mats; Curdt, W.; Davenne, J.; Davila, J.; DeForest, C. E.; Del Zanna, Giulio; Drummond, D.; Dubau, J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, Terje; Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest, S.; Gyo, M.; Haberreiter, M.; Hansteen, Viggo; Harrison, R.; Hassler, D. M.; Haugan, Stein Vidar Hagfors; Howe, C.; Janvier, M.; Klein, R.; Koller, S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall, G.; Matthews, Sharon A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris, N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.; Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.; Sawyer, C.; Schlatter, P.; Schmutz, W.; Schüle, U.; Shaughnessy, B.; Sidher, S.; Solanki, Sami K.; Speight, R.; Spescha, M.; Szwec, N.; Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial, J.-C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, Robert F.; Woodward, S.; Young, P.; De Groof, A.; Pacros, A.; Williams, D.; Müller, Daniel (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    Aims. The Spectral Imaging of the Coronal Environment (SPICE) instrument is a high-resolution imaging spectrometer operating at extreme ultraviolet wavelengths. In this paper, we present the concept, design, and pre-launch ...
  • Three-dimensional modeling of the Ca II H and K lines in the solar atmosphere 
    Bjørgen, Johan pires; Sukhorukov, Andrii V.; Leenaarts, Jorrit; Carlsson, Mats; de la Cruz Rodriguez, Jaime; Scharmer, Göran B.; Hansteen, Viggo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    Context: CHROMIS, a new imaging spectrometer at the Swedish 1-m Solar Telescope (SST), can observe the chromosphere in the H and K lines of Ca II at high spatial and spectral resolution. Accurate modeling as well as an ...
  • TIME DEPENDENT NONEQUILIBRIUM IONIZATION of TRANSITION REGION LINES OBSERVED with IRIS 
    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 ...
  • Two-dimensional Radiative Magnetohydrodynamic Simulations of Partial Ionization in the Chromosphere. II. Dynamics and Energetics of the Low Solar Atmosphere 
    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 ...