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Author Ko, Yuan-Kuen ♦ Warren, Harry P. ♦ Ugarte-Urra, Ignacio ♦ Young, Peter R. ♦ Muglach, Karin
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ ABUNDANCE ♦ COMPARATIVE EVALUATIONS ♦ CORRELATIONS ♦ DENSITY ♦ ELECTRON DENSITY ♦ ELECTRON TEMPERATURE ♦ ELECTRONS ♦ EMISSION ♦ EXTREME ULTRAVIOLET RADIATION ♦ HOT PLASMA ♦ IONIZATION POTENTIAL ♦ MAGNETIC FIELDS ♦ SOLAR CORONA ♦ SPECTROMETERS ♦ STAR EVOLUTION ♦ SUN
Abstract We present the analysis of a decaying active region observed by the EUV Imaging Spectrometer on Hinode during 2009 December 7–11. We investigated the temporal evolution of its structure exhibited by plasma at temperatures from 300,000 to 2.8 million degrees, and derived the electron density, differential emission measure, effective electron temperature, and elemental abundance ratios of Si/S and Fe/S (as a measure of the First Ionization Potential (FIP) Effect). We compared these coronal properties to the temporal evolution of the photospheric magnetic field strength obtained from the Solar and Heliospheric Observatory Michelson Doppler Imager magnetograms. We find that, while these coronal properties all decreased with time during this decay phase, the largest change was at plasma above 1.5 million degrees. The photospheric magnetic field strength also decreased with time but mainly for field strengths lower than about 70 Gauss. The effective electron temperature and the FIP bias seem to reach a “basal” state (at 1.5 × 10{sup 6} K and 1.5, respectively) into the quiet Sun when the mean photospheric magnetic field (excluding all areas <10 G) weakened to below 35 G, while the electron density continued to decrease with the weakening field. These physical properties are all positively correlated with each other and the correlation is the strongest in the high-temperature plasma. Such correlation properties should be considered in the quest for our understanding of how the corona is heated. The variations in the elemental abundance should especially be considered together with the electron temperature and density.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2016-08-01
Publisher Place United States
Journal Astrophysical Journal
Volume Number 826
Issue Number 2


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