HINODE OBSERVATION OF PHOTOSPHERIC MAGNETIC ACTIVITIES TRIGGERING X-RAY MICROFLARES AROUND A WELL-DEVELOPED SUNSPOT
- National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa 252-5210 (Japan)
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.
- OSTI ID:
- 21460054
- Journal Information:
- Astrophysical Journal, Vol. 720, Issue 2; Other Information: DOI: 10.1088/0004-637X/720/2/1136; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
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