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Thermodynamic Spectrum of Solar Flares Based on SDO/EVE Observations: Techniques and First ResultsThe Solar Dynamics Observatory (SDO)/EUV Variability Experiment (EVE) provides rich information on the thermodynamic processes of solar activities, particularly on solar flares. Here, we develop a method to construct thermodynamic spectrum (TDS) charts based on the EVE spectral lines. This tool could potentially be useful for extreme ultraviolet (EUV) astronomy to learn about the eruptive activities on distant astronomical objects. Through several cases, we illustrate what we can learn from the TDS charts. Furthermore, we apply the TDS method to 74 flares equal to or greater than the M5.0 class, and reach the following statistical results. First, EUV peaks are always behind the soft X-ray (SXR) peaks and stronger flares tend to have faster cooling rates. There is a power-law correlation between the peak delay times and the cooling rates, suggesting a coherent cooling process of flares from SXR to EUV emissions. Second, there are two distinct temperature drift patterns, called Type I and Type II. For Type I flares, the enhanced emission drifts from high to low temperature like a quadrilateral, whereas for Type II flares the drift pattern looks like a triangle. Statistical analysis suggests that Type II flares are more impulsive than Type I flares. Third, for late-phase flares, the peak intensity ratio of the late phase to the main phase is roughly correlated with the flare class, and the flares with a strong late phase are all confined. We believe that the re-deposition of the energy carried by a flux rope, which unsuccessfully erupts out, into thermal emissions is responsible for the strong late phase found in a confined flare. Furthermore, we show the signatures of the flare thermodynamic process in the chromosphere and transition region in the TDS charts. These results provide new clues to advance our understanding of the thermodynamic processes of solar flares and associated solar eruptions, e.g., coronal mass ejections.
Document ID
20170003754
Document Type
Reprint (Version printed in journal)
Authors
Wang, Yuming (China Scientific and Technical Univ. Hofei, China)
Zhou, Zhenjun (China Scientific and Technical Univ. Hofei, China)
Zhang, Jie (George Mason Univ. Fairfax, VA, United States)
Liu, Kai (China Scientific and Technical Univ. Hofei, China)
Liu, Rui (China Scientific and Technical Univ. Hofei, China)
Shen, Chenglong (China Scientific and Technical Univ. Hofei, China)
Chamberlin, Phillip C. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
April 20, 2017
Publication Date
March 9, 2016
Publication Information
Publication: The Astrophysical Journal: Supplement Series
Volume: 223
Issue: 1
ISSN: 0067-0049
Subject Category
Solar Physics
Astronomy
Report/Patent Number
GSFC-E-DAA-TN41037
Distribution Limits
Public
Copyright
Other