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Title: Chromospheric Plasma Ejections in a Light Bridge of a Sunspot

Abstract

It is well-known that light bridges (LBs) inside a sunspot produce small-scale plasma ejections and transient brightenings in the chromosphere, but the nature and origin of such phenomena are still unclear. Utilizing the high-spatial and high-temporal resolution spectral data taken with the Fast Imaging Solar Spectrograph and the TiO 7057 Å broadband filter images installed at the 1.6 m New Solar Telescope of Big Bear Solar Observatory, we report arcsecond-scale chromospheric plasma ejections (1.″7) inside a LB. Interestingly, the ejections are found to be a manifestation of upwardly propagating shock waves as evidenced by the sawtooth patterns seen in the temporal-spectral plots of the Ca ii 8542 Å and H α intensities. We also found a fine-scale photospheric pattern (1″) diverging with a speed of about 2 km s{sup −1} two minutes before the plasma ejections, which seems to be a manifestation of magnetic flux emergence. As a response to the plasma ejections, the corona displayed small-scale transient brightenings. Based on our findings, we suggest that the shock waves can be excited by the local disturbance caused by magnetic reconnection between the emerging flux inside the LB and the adjacent umbral magnetic field. The disturbance generates slow-mode waves, which soonmore » develop into shock waves, and manifest themselves as the arcsecond-scale plasma ejections. It also appears that the dissipation of mechanical energy in the shock waves can heat the local corona.« less

Authors:
; ; ; ;  [1];  [2]; ;  [3]
  1. Astronomy Program, Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826 (Korea, Republic of)
  2. Big Bear Solar Observatory, New Jersey Institute of Technology, 40386 North Shore Lane, Big Bear City, CA 92314-9672 (United States)
  3. Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Yuseong-gu, Daejeon 34055 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22663910
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 835; 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; CHROMOSPHERE; DISTURBANCES; FILTERS; HEAT; MAGNETIC FIELDS; MAGNETIC FLUX; MAGNETIC RECONNECTION; PHOTOSPHERE; PLASMA; PLASMA INSTABILITY; RESOLUTION; SAWTOOTH OSCILLATIONS; SHOCK WAVES; SUN; SUNSPOTS; TELESCOPES; TITANIUM OXIDES; TRANSIENTS; VELOCITY; VISIBLE RADIATION

Citation Formats

Song, Donguk, Chae, Jongchul, Yang, Heesu, Cho, Kyuhyoun, Kwak, Hannah, Yurchyshyn, Vasyl, Lim, Eun-Kyung, and Cho, Kyung-Suk, E-mail: dusong@astro.snu.ac.kr. Chromospheric Plasma Ejections in a Light Bridge of a Sunspot. United States: N. p., 2017. Web. doi:10.3847/1538-4357/835/2/240.
Song, Donguk, Chae, Jongchul, Yang, Heesu, Cho, Kyuhyoun, Kwak, Hannah, Yurchyshyn, Vasyl, Lim, Eun-Kyung, & Cho, Kyung-Suk, E-mail: dusong@astro.snu.ac.kr. Chromospheric Plasma Ejections in a Light Bridge of a Sunspot. United States. doi:10.3847/1538-4357/835/2/240.
Song, Donguk, Chae, Jongchul, Yang, Heesu, Cho, Kyuhyoun, Kwak, Hannah, Yurchyshyn, Vasyl, Lim, Eun-Kyung, and Cho, Kyung-Suk, E-mail: dusong@astro.snu.ac.kr. Wed . "Chromospheric Plasma Ejections in a Light Bridge of a Sunspot". United States. doi:10.3847/1538-4357/835/2/240.
@article{osti_22663910,
title = {Chromospheric Plasma Ejections in a Light Bridge of a Sunspot},
author = {Song, Donguk and Chae, Jongchul and Yang, Heesu and Cho, Kyuhyoun and Kwak, Hannah and Yurchyshyn, Vasyl and Lim, Eun-Kyung and Cho, Kyung-Suk, E-mail: dusong@astro.snu.ac.kr},
abstractNote = {It is well-known that light bridges (LBs) inside a sunspot produce small-scale plasma ejections and transient brightenings in the chromosphere, but the nature and origin of such phenomena are still unclear. Utilizing the high-spatial and high-temporal resolution spectral data taken with the Fast Imaging Solar Spectrograph and the TiO 7057 Å broadband filter images installed at the 1.6 m New Solar Telescope of Big Bear Solar Observatory, we report arcsecond-scale chromospheric plasma ejections (1.″7) inside a LB. Interestingly, the ejections are found to be a manifestation of upwardly propagating shock waves as evidenced by the sawtooth patterns seen in the temporal-spectral plots of the Ca ii 8542 Å and H α intensities. We also found a fine-scale photospheric pattern (1″) diverging with a speed of about 2 km s{sup −1} two minutes before the plasma ejections, which seems to be a manifestation of magnetic flux emergence. As a response to the plasma ejections, the corona displayed small-scale transient brightenings. Based on our findings, we suggest that the shock waves can be excited by the local disturbance caused by magnetic reconnection between the emerging flux inside the LB and the adjacent umbral magnetic field. The disturbance generates slow-mode waves, which soon develop into shock waves, and manifest themselves as the arcsecond-scale plasma ejections. It also appears that the dissipation of mechanical energy in the shock waves can heat the local corona.},
doi = {10.3847/1538-4357/835/2/240},
journal = {Astrophysical Journal},
number = 2,
volume = 835,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2017},
month = {Wed Feb 01 00:00:00 EST 2017}
}