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Title: HINODE OBSERVATION OF PHOTOSPHERIC MAGNETIC ACTIVITIES TRIGGERING X-RAY MICROFLARES AROUND A WELL-DEVELOPED SUNSPOT

Abstract

Microflares, which are small energetic events in the solar corona, are an example of dynamical phenomena suitable for understanding energy release processes in the solar corona. We identified 55 microflares around a well-developed sunspot surrounded by a moat with high-cadence X-ray images from the Hinode X-ray Telescope, and searched for their photospheric counterparts in line-of-sight magnetograms taken with the Hinode Solar Optical Telescope. We found opposite magnetic polarities encountering each other around the footpoints of 28 microflares, while we could not find such encounters around the footpoints of the other 27 microflares. Emerging magnetic fluxes in the moat were the dominant origin causing the encounters of opposite polarities (21 of 28 events). Unipolar moving magnetic features (MMFs) with negative polarities the same as the sunspot definitely caused the encounters of opposite polarities for five microflares. The decrease of magnetic flux, i.e., magnetic flux cancellation, was confirmed at the encountering site in typical examples of microflares. Microflares were not isotropically distributed around the spot; the microflares with emerging magnetic fluxes (EMFs) were observed in the direction where magnetic islands with the same polarity as the spot were located at the outer boundary of the moat, while the microflares with negative MMFsmore » were observed in the direction where magnetic islands with polarity opposite to the spot were located at the outer boundary of the moat. We also found that EMFs in the moat had a unique orientation in which those with the same polarity as the spot is closer to the spot than the other one that had the opposite polarity to the spot. These observational results lead to two magnetic configurations including magnetic reconnection for triggering energy release at least in half of the microflares around the spot, and suggest that the global magnetic structures around the spot strongly affect what kinds of polarity encounters are formed in the sunspot moat.« less

Authors:
 [1];  [2]
  1. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
  2. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa 252-5210 (Japan)
Publication Date:
OSTI Identifier:
21460054
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 720; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/720/2/1136; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ELECTROMOTIVE FORCE; GAMMA RADIATION; MAGNETIC FLUX; MAGNETIC ISLANDS; MAGNETIC RECONNECTION; PHOTOSPHERE; SOLAR CORONA; SUN; SUNSPOTS; TELESCOPES; ATMOSPHERES; ELECTROMAGNETIC RADIATION; IONIZING RADIATIONS; MAGNETIC FIELD CONFIGURATIONS; MAIN SEQUENCE STARS; RADIATIONS; SOLAR ACTIVITY; SOLAR ATMOSPHERE; STARS; STARSPOTS; STELLAR ACTIVITY; STELLAR ATMOSPHERES; STELLAR CORONAE

Citation Formats

Kano, R, Shimizu, T, and Tarbell, T. D., E-mail: ryouhei.kano@nao.ac.j. HINODE OBSERVATION OF PHOTOSPHERIC MAGNETIC ACTIVITIES TRIGGERING X-RAY MICROFLARES AROUND A WELL-DEVELOPED SUNSPOT. United States: N. p., 2010. Web. doi:10.1088/0004-637X/720/2/1136.
Kano, R, Shimizu, T, & Tarbell, T. D., E-mail: ryouhei.kano@nao.ac.j. HINODE OBSERVATION OF PHOTOSPHERIC MAGNETIC ACTIVITIES TRIGGERING X-RAY MICROFLARES AROUND A WELL-DEVELOPED SUNSPOT. United States. https://doi.org/10.1088/0004-637X/720/2/1136
Kano, R, Shimizu, T, and Tarbell, T. D., E-mail: ryouhei.kano@nao.ac.j. 2010. "HINODE OBSERVATION OF PHOTOSPHERIC MAGNETIC ACTIVITIES TRIGGERING X-RAY MICROFLARES AROUND A WELL-DEVELOPED SUNSPOT". United States. https://doi.org/10.1088/0004-637X/720/2/1136.
@article{osti_21460054,
title = {HINODE OBSERVATION OF PHOTOSPHERIC MAGNETIC ACTIVITIES TRIGGERING X-RAY MICROFLARES AROUND A WELL-DEVELOPED SUNSPOT},
author = {Kano, R and Shimizu, T and Tarbell, T. D., E-mail: ryouhei.kano@nao.ac.j},
abstractNote = {Microflares, which are small energetic events in the solar corona, are an example of dynamical phenomena suitable for understanding energy release processes in the solar corona. We identified 55 microflares around a well-developed sunspot surrounded by a moat with high-cadence X-ray images from the Hinode X-ray Telescope, and searched for their photospheric counterparts in line-of-sight magnetograms taken with the Hinode Solar Optical Telescope. We found opposite magnetic polarities encountering each other around the footpoints of 28 microflares, while we could not find such encounters around the footpoints of the other 27 microflares. Emerging magnetic fluxes in the moat were the dominant origin causing the encounters of opposite polarities (21 of 28 events). Unipolar moving magnetic features (MMFs) with negative polarities the same as the sunspot definitely caused the encounters of opposite polarities for five microflares. The decrease of magnetic flux, i.e., magnetic flux cancellation, was confirmed at the encountering site in typical examples of microflares. Microflares were not isotropically distributed around the spot; the microflares with emerging magnetic fluxes (EMFs) were observed in the direction where magnetic islands with the same polarity as the spot were located at the outer boundary of the moat, while the microflares with negative MMFs were observed in the direction where magnetic islands with polarity opposite to the spot were located at the outer boundary of the moat. We also found that EMFs in the moat had a unique orientation in which those with the same polarity as the spot is closer to the spot than the other one that had the opposite polarity to the spot. These observational results lead to two magnetic configurations including magnetic reconnection for triggering energy release at least in half of the microflares around the spot, and suggest that the global magnetic structures around the spot strongly affect what kinds of polarity encounters are formed in the sunspot moat.},
doi = {10.1088/0004-637X/720/2/1136},
url = {https://www.osti.gov/biblio/21460054}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 720,
place = {United States},
year = {Fri Sep 10 00:00:00 EDT 2010},
month = {Fri Sep 10 00:00:00 EDT 2010}
}