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Solar Physics

, Volume 291, Issue 1, pp 67–87 | Cite as

Observed IRIS Profiles of the h and k Doublet of Mg ii and Comparison with Profiles from Quiescent Prominence NLTE Models

  • Jean-Claude Vial
  • Gabriel Pelouze
  • Petr Heinzel
  • Lucia Kleint
  • Ulrich Anzer
Article

Abstract

With the launch of the Interface Region Imaging Spectrograph (IRIS) mission, it is now possible to obtain high-resolution solar prominence spectra and to begin to distinguish the contributions of the many (apparent or not) threads that structure prominences. We aim at comparing unique observations obtained in the Mg ii h and k lines of a polar crown prominence with the radiative outputs from one-dimensional models built with non-local-thermodynamic equilibrium codes (Heinzel et al. Astron. Astrophys. 564, A132, 2014). We characterize the profiles obtained through thorough calibration procedures, with attention paid to the absolute values, full-width at half-maximum, and the ratio of k to h intensities. We also show that at the top of some structures, line-of-sight velocities of about \(9~\mbox{km}\,\mbox{s}^{-1}\) can be detected. We find a range of static, low-pressure, low-thickness, low-temperature models that could fit k or h observed values, but that cannot satisfy the low observed k/h ratio. We investigate whether these low values might be explained by the inclusion of horizontal flows in small-scale threads. These flows are also necessary in another class of models, where the pressure is kept low but thickness and temperature are increased up to the observed thickness and up to 15 000 K.

Keywords

Mg ii lines Non-LTE diagnostic Sun prominences UV spectroscopy 

Notes

Acknowledgements

IRIS is a NASA small explorer mission developed and operated by LMSAL with mission operations executed at NASA Ames Research center and major contributions to downlink communications funded by the Norwegian Space Center (NSC, Norway) through an ESA PRODEX contract. EUVI/STEREO data are available at http://stereo-ssc.nascom.nasa.gov . AIA/SDO data are available at http://sdo.gsfc.nasa.gov/data/aiahmi . We acknowledge the use of full-disk H\(\upalpha\) data from El Teide ( http://gong.nso.edu ) and the Pic du Midi coronagrams ( http://www.climso.fr ). We also acknowledge the use of full-disk H\(\upalpha\) data from the Big Bear Solar Observatory, New Jersey Institute of Technology, kindly provided by V. Yurchyshyn. The authors thank A. Title for drawing their attention to these unique observations and for his help. They are deeply indebted to J.-P. Wuelser for his very helpful advice on the calibration issues and for providing unpublished data. They also thank J. Gurman and P. Lemaire for discussions on the photometry issues. The authors deeply thank both referees for their useful corrections and suggestions that contributed to the improvement of the article. P. Heinzel was supported by the project RVO:67985815 of the Astronomical Institute of the Czech Academy of Sciences.

Disclosure of Potential Conflict of Interest

The authors declare that they have no conflicts of interest.

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Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  • Jean-Claude Vial
    • 1
  • Gabriel Pelouze
    • 1
  • Petr Heinzel
    • 2
  • Lucia Kleint
    • 3
  • Ulrich Anzer
    • 4
  1. 1.Institut d’Astrophysique SpatialeCNRS (UMR 8617) Université Paris-Sud 11OrsayFrance
  2. 2.Astronomical InstituteCzech Academy of SciencesOndrejovCzech Republic
  3. 3.University of Applied Sciences and Arts Northwestern SwitzerlandWindischSwitzerland
  4. 4.Max-Planck-Institut fur AstrophysikGarchingGermany

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