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Title: TEMPORAL EVOLUTION OF VELOCITY AND MAGNETIC FIELD IN AND AROUND UMBRAL DOTS

Abstract

We study the temporal evolution of umbral dots (UDs) using measurements from the CRISP imaging spectropolarimeter at the Swedish 1 m Solar Telescope. Scans of the magnetically sensitive 630 nm iron lines were performed under stable atmospheric conditions for 71 minutes with a cadence of 63 s. These observations allow us to investigate the magnetic field and velocity in and around UDs at a resolution approaching 0.''13. From the analysis of 339 UDs, we draw the following conclusions: (1) UDs show clear hints of upflows, as predicted by magnetohydrodynamic simulations. By contrast, we could not find systematic downflow signals. Only in very deep layers, we detect localized downflows around UDs, but they do not persist in time. (2) We confirm that UDs exhibit weaker and more inclined fields than their surroundings, as reported previously. However, UDs that have strong fields above 2000 G or are in the decay phase show enhanced and more vertical fields. (3) There are enhanced fields at the migration front of UDs detached from penumbral grains, as if their motion were impeded by the ambient field. (4) Long-lived UDs travel longer distances with slower proper motions. Our results appear to confirm some aspects of recent numericalmore » simulations of magnetoconvection in the umbra (e.g., the existence of upflows in UDs), but not others (e.g., the systematic weakening of the magnetic field at the position of UDs).« less

Authors:
 [1];  [2]
  1. Unit of Synergetic Studies for Space, Kyoto University, 17 Kitakazan Ohmine-cho, Yamashina-ku, Kyoto 607-8417 (Japan)
  2. Instituto de Astrofisica de Andalucia (CSIC), Apartado de Correos 3004, E-18080 Granada (Spain)
Publication Date:
OSTI Identifier:
22092243
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 757; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; COMPUTERIZED SIMULATION; CONVECTION; DISTANCE; IRON; MAGNETIC FIELDS; POLARIMETRY; PROPER MOTION; RESOLUTION; SOLAR CORONA; SUN; SUNSPOTS; TELESCOPES

Citation Formats

Watanabe, Hiroko, Bellot Rubio, Luis R., De la Cruz Rodriguez, Jaime, and Rouppe van der Voort, Luc, E-mail: watanabe@kwasan.kyoto-u.ac.jp. TEMPORAL EVOLUTION OF VELOCITY AND MAGNETIC FIELD IN AND AROUND UMBRAL DOTS. United States: N. p., 2012. Web. doi:10.1088/0004-637X/757/1/49.
Watanabe, Hiroko, Bellot Rubio, Luis R., De la Cruz Rodriguez, Jaime, & Rouppe van der Voort, Luc, E-mail: watanabe@kwasan.kyoto-u.ac.jp. TEMPORAL EVOLUTION OF VELOCITY AND MAGNETIC FIELD IN AND AROUND UMBRAL DOTS. United States. https://doi.org/10.1088/0004-637X/757/1/49
Watanabe, Hiroko, Bellot Rubio, Luis R., De la Cruz Rodriguez, Jaime, and Rouppe van der Voort, Luc, E-mail: watanabe@kwasan.kyoto-u.ac.jp. 2012. "TEMPORAL EVOLUTION OF VELOCITY AND MAGNETIC FIELD IN AND AROUND UMBRAL DOTS". United States. https://doi.org/10.1088/0004-637X/757/1/49.
@article{osti_22092243,
title = {TEMPORAL EVOLUTION OF VELOCITY AND MAGNETIC FIELD IN AND AROUND UMBRAL DOTS},
author = {Watanabe, Hiroko and Bellot Rubio, Luis R. and De la Cruz Rodriguez, Jaime and Rouppe van der Voort, Luc, E-mail: watanabe@kwasan.kyoto-u.ac.jp},
abstractNote = {We study the temporal evolution of umbral dots (UDs) using measurements from the CRISP imaging spectropolarimeter at the Swedish 1 m Solar Telescope. Scans of the magnetically sensitive 630 nm iron lines were performed under stable atmospheric conditions for 71 minutes with a cadence of 63 s. These observations allow us to investigate the magnetic field and velocity in and around UDs at a resolution approaching 0.''13. From the analysis of 339 UDs, we draw the following conclusions: (1) UDs show clear hints of upflows, as predicted by magnetohydrodynamic simulations. By contrast, we could not find systematic downflow signals. Only in very deep layers, we detect localized downflows around UDs, but they do not persist in time. (2) We confirm that UDs exhibit weaker and more inclined fields than their surroundings, as reported previously. However, UDs that have strong fields above 2000 G or are in the decay phase show enhanced and more vertical fields. (3) There are enhanced fields at the migration front of UDs detached from penumbral grains, as if their motion were impeded by the ambient field. (4) Long-lived UDs travel longer distances with slower proper motions. Our results appear to confirm some aspects of recent numerical simulations of magnetoconvection in the umbra (e.g., the existence of upflows in UDs), but not others (e.g., the systematic weakening of the magnetic field at the position of UDs).},
doi = {10.1088/0004-637X/757/1/49},
url = {https://www.osti.gov/biblio/22092243}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 757,
place = {United States},
year = {Thu Sep 20 00:00:00 EDT 2012},
month = {Thu Sep 20 00:00:00 EDT 2012}
}