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

Now showing items 1-20 of 39

  • ALMA observations of transient heating in a solar active region 
    da Silva Santos, João Manuel; de la Cruz Rodriguez, Jaime; White, S. M.; Leenaarts, Jorrit; Vissers, Gregal Joan Maria; Hansteen, Viggo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    Aims. We aim to investigate the temperature enhancements and formation heights of solar active-region brightenings such as Ellerman bombs (EBs), ultraviolet bursts (UVBs), and flaring active-region fibrils (FAFs) using ...
  • Bombs and Flares at the Surface and Lower Atmosphere of the Sun 
    Hansteen, Viggo; Archontis, Vasilis; Mendes Domingos Pereira, Tiago; Carlsson, Mats; Rouppe van der Voort, Luc; Leenaarts, Jorrit (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
    A spectacular manifestation of solar activity is the appearance of transient brightenings in the far wings of the Hα line, known as Ellerman bombs (EBs). Recent observations obtained by the Interface Region Imaging ...
  • Chromospheric counterparts of solar transition region unresolved fine structure loops 
    Mendes Domingos Pereira, Tiago; Rouppe van der Voort, Luc; Hansteen, Viggo; De Pontieu, Bart Walter (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    Low-lying loops have been discovered at the solar limb in transition region temperatures by the Interface Region Imaging Spectrograph (IRIS). They do not appear to reach coronal temperatures, and it has been suggested that ...
  • CLUSTERS OF SMALL ERUPTIVE FLARES PRODUCED BY MAGNETIC RECONNECTION IN THE SUN 
    Archontis, Vasilis; Hansteen, Viggo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
    We report on the formation of small solar flares produced by patchy magnetic reconnection between interacting magnetic loops. A three-dimensional (3D) magnetohydrodynamic (MHD) numerical experiment was performed, where a ...
  • THE CYCLING OF MATERIAL BETWEEN THE SOLAR CORONA AND CHROMOSPHERE 
    Guerreiro, Nuno Miguel Rodrigues; Hansteen, Viggo; De Pontieu, Bart (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2013)
    Observations of transition region emission lines reveal the presence of redshifts in lines formed from the top of the chromosphere up to temperatures of about 2.5 × 105 K and blueshifts for temperatures above that. However, ...
  • A DETAILED COMPARISON BETWEEN THE OBSERVED AND SYNTHESIZED PROPERTIES OF A SIMULATED TYPE II SPICULE 
    Martinez-Sykora, Juan; De Pontieu, Bart Walter; Leenaarts, Jorrit; Pereira, Tiago Mendes Domingos; Carlsson, Mats; Hansteen, Viggo; Stern, J. V.; Tian, H; McIntosh, S.W.; Rouppe, Van Der Voort Luc (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2013)
    We have performed a three-dimensional radiative MHD simulation of the solar atmosphere. This simulation shows a jet-like feature that shows similarities to the type II spicules observed for the first time with Hinode's ...
  • Detection of supersonic downflows and associated heating events in the transition region above sunspots 
    Kleint, L.; Antolin, Patrick; Tian, H; Judge, Philip G.; Testa, Paola; De Pontieu, Bart Walter; Martinez-Sykora, Juan; Reeves, K. K.; Wuelser, J. P.; McKillop, S.; Saar, S.; Carlsson, Mats; Boerner, P.; Hurlburt, N.; Lemen, J.; Tarbell, T.D.; Title, A.; Golub, L.; Hansteen, Viggo; Jaeggli, S.; Kankelborg, C. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
    Interface Region Imaging Spectrograph data allow us to study the solar transition region (TR) with an unprecedented spatial resolution of 0farcs33. On 2013 August 30, we observed bursts of high Doppler shifts suggesting ...
  • Disentangling flows in the solar transition region 
    Zacharias, Pia; Hansteen, Viggo; Leenaarts, Jorrit; Carlsson, Mats; Gudiksen, Boris Vilhelm (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    Context: The measured average velocities in solar and stellar spectral lines formed at transition region temperatures have been difficult to interpret. The dominant redshifts observed in the lower transition region naturally ...
  • Ellerman bombs and UV bursts: reconnection at different atmospheric layers 
    Ortiz, Ada; Hansteen, Viggo; Nóbrega Siverio, Daniel Elias; Rouppe van der Voort, Luc (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    The emergence of magnetic flux through the photosphere and into the outer solar atmosphere produces, amongst other dynamical phenomena, Ellerman bombs (EBs), which are observed in the wings of Hα and are due to magnetic ...
  • Ellerman bombs and UV bursts: reconnection at different atmospheric layers 
    Ortiz, Ada; Hansteen, Viggo; Nóbrega Siverio, Daniel Elias; van der Voort, Luc Rouppe (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    The emergence of magnetic flux through the photosphere and into the outer solar atmosphere produces, amongst other dynamical phenomena, Ellerman bombs (EBs), which are observed in the wings of Hα and are due to magnetic ...
  • Ellerman bombs and UV bursts: transient events in chromospheric current sheets 
    Hansteen, Viggo; Ortiz, Ada; Archontis, Vasilis; Carlsson, Mats; Mendes Domingos Pereira, Tiago; Bjørgen, Johan Pires (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2019)
    Context: Ellerman bombs (EBs), observed in the photospheric wings of the Hα line, and UV bursts, observed in the transition region Si IV line, are both brightenings related to flux emergence regions and specifically to ...
  • EMERGENCE OF GRANULAR-SIZED MAGNETIC BUBBLES THROUGH THE SOLAR ATMOSPHERE. I. SPECTROPOLARIMETRIC OBSERVATIONS AND SIMULATIONS 
    Ortiz, Ada; Bellot Rubio, L. R.; Hansteen, Viggo; de la Cruz Rodriguez, Jaime; Rouppe, Van Der Voort Luc (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
    We study a granular-sized magnetic flux emergence event that occurred in NOAA 11024 in 2009 July. The observations were made with the CRISP spectropolarimeter at the Swedish 1 m Solar Telescope achieving a spatial resolution ...
  • EMERGENCE of GRANULAR-SIZED MAGNETIC BUBBLES THROUGH the SOLAR ATMOSPHERE. II. NON-LTE CHROMOSPHERIC DIAGNOSTICS and INVERSIONS 
    de la Cruz Rodriguez, Jaime; Hansteen, Viggo; Bellot-Rubio, Luis; Ortiz, Ada (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    Magnetic flux emergence into the outer layers of the Sun is a fundamental mechanism for releasing energy into the chromosphere and the corona. In this paper, we study the emergence of granular-sized flux concentrations and ...
  • Emergence of Granular-Sized Magnetic Bubbles through the Solar Atmosphere. III. The Path to the Transition Region 
    Ortiz, Ada; Hansteen, Viggo; Bellot Rubio, L. R.; de la Cruz Rodriguez, Jaime; De Pontieu, Bart Walter; Carlsson, Mats; Rouppe, Van Der Voort Luc (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
    We study, for the first time, the ascent of granular-sized magnetic bubbles from the solar photosphere through the chromosphere into the transition region and above. Such events occurred in a flux emerging region in NOAA ...
  • THE FORMATION of IRIS DIAGNOSTICS. IV. the Mg ii TRIPLET LINES AS A NEW DIAGNOSTIC FOR LOWER CHROMOSPHERIC HEATING 
    Mendes Domingos Pereira, Tiago; Carlsson, Mats; De Pontieu, Bart Walter; Hansteen, Viggo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    A triplet of subordinate lines of Mg ii exists in the region around the h&k lines. In solar spectra these lines are seen mostly in absorption, but in some cases can become emission lines. The aim of this work is to study ...
  • Heating signatures in the disk counterparts of solar spicules in interface region imaging spectrograph observations 
    Rouppe, Van Der Voort Luc; De Pontieu, Bart Walter; Mendes Domingos Pereira, Tiago; Carlsson, Mats; Hansteen, Viggo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    We use coordinated observations with the Interface Region Imaging Spectrograph (IRIS) and the Swedish 1 m Solar Telescope to identify the disk counterpart of type II spicules in upper-chromospheric and transition region ...
  • HIGH-RESOLUTION OBSERVATIONS OF THE SHOCK WAVE BEHAVIOR FOR SUNSPOT OSCILLATIONS WITH THE INTERFACE REGION IMAGING SPECTROGRAPH 
    Tian, H; DeLuca, E.; Reeves, K. K.; McKillop, S.; De Pontieu, Bart Walter; Martinez-Sykora, Juan; Carlsson, Mats; Hansteen, Viggo; Kleint, L.; Cheung, M; Golub, L.; Saar, S.; Testa, Paola; Weber, M.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T.D.; Wuelser, J. P.; Kankelborg, C.; Jaeggli, S.; McIntosh, S.W. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
    We present the first results of sunspot oscillations from observations by the Interface Region Imaging Spectrograph. The strongly nonlinear oscillation is identified in both the slit-jaw images and the spectra of several ...
  • High-resolution observations of the solar photosphere, chromosphere, and transition region: A database of coordinated IRIS and SST observations 
    Rouppe van der Voort, Luc; De Pontieu, Bart Walter; Carlsson, Mats; de la Cruz Rodriguez, Jaime; Bose, Souvik; Chintzoglou, Georgios; Drews, Ainar; Froment, Clara; Gošić, Milan; Graham, David R.; Hansteen, Viggo; de Jorge Henriques, Vasco Manuel; Jafarzadeh, Shahin; Joshi, Jayant; Kleint, Lucia; Kohutova, Petra; Leifsen, Torben; Martinez-Sykora, Juan; Nóbrega Siverio, Daniel Elias; Ortiz, Ada; Mendes Domingos Pereira, Tiago; Popovas, Andrius; Quintero Noda, Carlos; Sainz Dalda, Alberto; Scharmer, Göran B.; Schmit, Donald; Scullion, Eamon; Skogsrud, Håkon; Szydlarski, Mikolaj Marcin; Timmons, R.; Vissers, Gregal Joan Maria; Woods, M. M.; Zacharias, Pia (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    NASA’s Interface Region Imaging Spectrograph (IRIS) provides high-resolution observations of the solar atmosphere through ultraviolet spectroscopy and imaging. Since the launch of IRIS in June 2013, we have conducted ...
  • Homologous helical jets: Observations by IRIS, SDO, and Hinode and magnetic modeling with data-driven simulations 
    Cheung, Mark C. M.; De Pontieu, Bart Walter; Tarbell, Theodore D.; Fu, Y.; Tian, H.; Testa, Paola; Reeves, K. K.; Martinez-Sykora, Juan; Boerner, P.; Wulser, J. P.; Lemen, J.; Title, Alan M.; Hurlburt, N.; Kleint, L.; Kankelborg, C.; Jaeggli, S.; Golub, L.; McKillop, S.; Saar, S.; Carlsson, Mats; Hansteen, Viggo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    We report on observations of recurrent jets by instruments on board the Interface Region Imaging Spectrograph, Solar Dynamics Observatory (SDO), and Hinode spacecraft. Over a 4 hr period on 2013 July 21, recurrent coronal ...
  • Impact of Type II Spicules in the Corona: Simulations and Synthetic Observables 
    Martinez-Sykora, Juan; De Moortel, Ineke; De Pontieu, Bart Walter; Hansteen, Viggo; Carlsson, Mats (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    The role of type II spicules in the corona has been a much debated topic in recent years. This paper aims to shed light on the impact of type II spicules in the corona using novel 2.5D radiative MHD simulations, including ...