Abstract
The 6 June 2007 16:55 UT flare was well observed with high time-cadence sparse raster scans by the EUV Imaging Spectrometer (EIS) on board the Hinode spacecraft. The observation covers an active region area of 240 arcsec × 240 arcsec with the 1 arcsec slit in about 160 seconds.
We describe here spectral properties of a “pre-flare brightening” to this flare, which started about nine minutes prior to flare-ribbon onset. This flare brightening looks like two small loops apparently having a cusp-shape structure about 40 – 50 arcsec west of the main flaring loops, which show dynamic behavior in velocity during the early phases of the flare: The He ii line at 256.32 Å shows the existence of a bi-directional flow along the Sun–Earth line of sight of about −70 and +100 km s−1. On the other hand, the Fe xvi line at 262.98 Å formed at higher coronal temperatures shows only a slight increase in intensity at the location of these loops, and the Fe xxiii line at 263.76 Å barely appears. Electron density at the site derived from the intensity ratios of the Fe xiv line pair at 264.78 Å and 274.20 Å is lower than the average of 109.3 cm−3 in other parts of the active-region outskirts. Combining a time series of STEREO-A/B SECCHI-EUVI 171 Å images, we conclude that the pre-flare-brightening region may be heated via magnetic reconnection taking place as a result of loop–loop interaction.
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Acknowledgements
Hinode is a Japanese mission developed and launched by ISAS/JAXA, collaborating with NAOJ as domestic partner, NASA and STFC (UK) as international partners. Scientific operation of the Hinode mission is conducted by the Hinode science team organized at ISAS/JAXA. This team mainly consists of scientists from institutes in the partner countries. Support for the post-launch operation is provided by JAXA and NAOJ (Japan), STFC (UK), NASA (USA), ESA, and NSC (Norway). This work is partly carried out at the NAOJ Hinode Science Center, which was supported by the Grant-in-Aid for Creative Scientific Research: “The Basic Study of Space Weather Prediction” from MEXT, Japan (Head Investigator: K. Shibata), generous donations from Sun Microsystems, and NAOJ/NINS internal funding. It was also supported by NINS inter-institute collaborative program for Creation of New Research Area (Head Investigator: T. Watanabe), and by NIFS/NINS under the project of Formation of International Network for Scientific Collaborations (Head Investigator: H. Yamada). ACS was supported by funding from NASA’s Office of Space Science through the Living with a Star and the Supporting Research and Technology programs.
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Guest Editors: Bernhard Fleck, Bernd Heber, and Angelos Vourlidas
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Watanabe, T., Hara, H., Sterling, A.C. et al. Production of High-Temperature Plasmas During the Early Phases of a C9.7 Flare. II. Bi-directional Flows Suggestive of Reconnection in a Pre-flare Brightening Region. Sol Phys 281, 87–99 (2012). https://doi.org/10.1007/s11207-012-0079-5
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DOI: https://doi.org/10.1007/s11207-012-0079-5