TWO TYPES OF EXTREME-ULTRAVIOLET BRIGHTENINGS IN AR 10926 OBSERVED BY HINODE/EIS

Journal Article · Wed Jul 20 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/736/1/15· OSTI ID:21578348

Lee, K -S ^[1]; Moon, Y -J; Choe, G S ^[2]; Kim, Sujin; Cho, Kyung-Suk ^[3]; Imada, S ^[4]

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1. Department of Astronomy and Space Science, Kyung Hee University, Yongin 446-701 (Korea, Republic of)
2. School of Space Research, Kyung Hee University, Yongin 446-701 (Korea, Republic of)
3. Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)
4. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara-shi, Kanagawa 252-5210 (Japan)

We have investigated seven extreme-ultraviolet (EUV) brightenings in the active region AR 10926 on 2006 December 2 observed by the EUV Imaging Spectrometer on board the Hinode spacecraft. We have determined their Doppler velocities and non-thermal velocities from 15 EUV spectral lines (log T = 4.7 - 6.4) by fitting each line profile to a Gaussian function. The Doppler velocity maps for different temperatures are presented to show the height dependence of the Doppler shifts. It is found that the active region brightenings show two distinct Doppler shift patterns. The type 1 brightening shows a systematic increase of Doppler velocity from -68 km s{sup -1} (strong blueshift) at log T = 4.7 to -2 km s{sup -1} (weak blueshift) at log T = 6.4, while the type 2 brightenings have Doppler velocities in the range from -20 km s{sup -1} to 20 km s{sup -1}. The type 1 brightening point is considered to sit in an upward reconnection outflow whose speed decreases with height. In both types of brightenings, the non-thermal velocity is found to be significantly enhanced at log T = 5.8 compared to the background region. We have also determined electron densities from line ratios and derived temperatures from emission measure loci using the CHIANTI atomic database. The electron densities of all brightenings are comparable to typical values in active regions (log N{sub e} = 9.9-10.4). The emission measure loci plots indicate that these brightenings should be multi-thermal whereas the background is isothermal. The differential emission measure as a function of temperature shows multiple peaks in the EUV brightening regions, while it has only a single peak (log T = 6.0) in the background region. Using Michelson Doppler Imager magnetograms, we have found that the type 1 brightening is associated with a canceling magnetic feature with a flux canceling rate of 2.4 x 10{sup 18} Mx hr{sup -1}. We also found the canceling magnetic feature and chromospheric brightenings in the type 1 brightening from the Hinode SOT and Transition Region and Coronal Explorer data. This observation corroborates our argument that brightening is caused by magnetic reconnection in a low atmosphere.

• OSTI ID: 21578348
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 736; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ATMOSPHERES
CHROMOSPHERE
DOPPLER EFFECT
ELECTROMAGNETIC RADIATION
ELECTRON DENSITY
EMISSION
EXTREME ULTRAVIOLET RADIATION
MAGNETIC RECONNECTION
RADIATIONS
SOLAR ATMOSPHERE
STELLAR ATMOSPHERES
TEMPERATURE DEPENDENCE
ULTRAVIOLET RADIATION
VELOCITY