skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A Hot Downflowing Model Atmosphere for Umbral Flashes and the Physical Properties of Their Dark Fibrils

Abstract

We perform non-LTE inversions in a large set of umbral flashes, including the dark fibrils visible within them, and in the quiescent umbra by using the inversion code NICOLE on a set of full Stokes high-resolution Ca ii λ 8542 observations of a sunspot at disk center. We find that the dark structures have Stokes profiles that are distinct from those of the quiescent and flashed regions. They are best reproduced by atmospheres that are more similar to the flashed atmosphere in terms of velocities, even if with reduced amplitudes. We also find two sets of solutions that finely fit the flashed profiles: a set that is upflowing, featuring a transition region that is deeper than in the quiescent case and preceded by a slight dip in temperature, and a second solution with a hotter atmosphere in the chromosphere but featuring downflows close to the speed of sound at such heights. Such downflows may be related, or even dependent, on the presence of coronal loops, rooted in the umbra of sunspots, as is the case in the region analyzed. Similar loops have been recently observed to have supersonic downflows in the transition region and are consistent with the earlier “sunspotmore » plumes,” which were invariably found to display strong downflows in sunspots. Finally, we find, on average, a magnetic field reduction in the flashed areas, suggesting that the shock pressure is moving field lines in the upper layers.« less

Authors:
;  [1];  [2];  [3]
  1. Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, BT7 1NN, Northern Ireland (United Kingdom)
  2. Instituto de Astrofísica de Canarias, Avda vía Láctea S/N, E-38205 La Laguna, Tenerife (Spain)
  3. Institute for Solar Physics, Department of Astronomy, Stockholm University, AlbaNova University Centre, SE-106 91 Stockholm (Sweden)
Publication Date:
OSTI Identifier:
22663241
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 845; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMPLITUDES; CHROMOSPHERE; LAYERS; MAGNETIC FIELDS; MATHEMATICAL SOLUTIONS; PHYSICAL PROPERTIES; PLUMES; RESOLUTION; SOUND WAVES; SUN; SUNSPOTS; VELOCITY

Citation Formats

Henriques, V. M. J., Mathioudakis, M., Socas-Navarro, H., and Rodríguez, J. de la Cruz, E-mail: v.henriques@qub.ac.uk. A Hot Downflowing Model Atmosphere for Umbral Flashes and the Physical Properties of Their Dark Fibrils. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA7CA4.
Henriques, V. M. J., Mathioudakis, M., Socas-Navarro, H., & Rodríguez, J. de la Cruz, E-mail: v.henriques@qub.ac.uk. A Hot Downflowing Model Atmosphere for Umbral Flashes and the Physical Properties of Their Dark Fibrils. United States. doi:10.3847/1538-4357/AA7CA4.
Henriques, V. M. J., Mathioudakis, M., Socas-Navarro, H., and Rodríguez, J. de la Cruz, E-mail: v.henriques@qub.ac.uk. Sun . "A Hot Downflowing Model Atmosphere for Umbral Flashes and the Physical Properties of Their Dark Fibrils". United States. doi:10.3847/1538-4357/AA7CA4.
@article{osti_22663241,
title = {A Hot Downflowing Model Atmosphere for Umbral Flashes and the Physical Properties of Their Dark Fibrils},
author = {Henriques, V. M. J. and Mathioudakis, M. and Socas-Navarro, H. and Rodríguez, J. de la Cruz, E-mail: v.henriques@qub.ac.uk},
abstractNote = {We perform non-LTE inversions in a large set of umbral flashes, including the dark fibrils visible within them, and in the quiescent umbra by using the inversion code NICOLE on a set of full Stokes high-resolution Ca ii λ 8542 observations of a sunspot at disk center. We find that the dark structures have Stokes profiles that are distinct from those of the quiescent and flashed regions. They are best reproduced by atmospheres that are more similar to the flashed atmosphere in terms of velocities, even if with reduced amplitudes. We also find two sets of solutions that finely fit the flashed profiles: a set that is upflowing, featuring a transition region that is deeper than in the quiescent case and preceded by a slight dip in temperature, and a second solution with a hotter atmosphere in the chromosphere but featuring downflows close to the speed of sound at such heights. Such downflows may be related, or even dependent, on the presence of coronal loops, rooted in the umbra of sunspots, as is the case in the region analyzed. Similar loops have been recently observed to have supersonic downflows in the transition region and are consistent with the earlier “sunspot plumes,” which were invariably found to display strong downflows in sunspots. Finally, we find, on average, a magnetic field reduction in the flashed areas, suggesting that the shock pressure is moving field lines in the upper layers.},
doi = {10.3847/1538-4357/AA7CA4},
journal = {Astrophysical Journal},
number = 2,
volume = 845,
place = {United States},
year = {Sun Aug 20 00:00:00 EDT 2017},
month = {Sun Aug 20 00:00:00 EDT 2017}
}