Thermodynamic Spectrum of Solar Flares Based on SDO/EVE Observations: Techniques and Statistical Results

Abstract

SDO/EVE provides rich information of the thermodynamic processes of solar activities, particularly of solar flares. Here, we develop a method to construct thermodynamic spectrum (TDS) charts based on the EVE spectral lines. This tool could be potentially useful to the EUV astronomy to learn the eruptive activities on the 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 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 a faster cooling rate. 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, that unsuccessfully erupts out, into thermal emissions is responsible for the strong late phase found in a confined flare. Besides, with some cases we illustrate the signatures of the flare thermodynamic process in the chromosphere and transition region in 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.

Submitted to ApJS, 43 pages, 22 figures, 5 tables

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• Extended relativistic configuration interaction and many-body perturbation calculations of spectroscopic data for the $n\le 6$ configurationsin ne-like ions between Cr XV and Kr XXVII
• On the Magnetic and Energy Characteristics of Recurrent Homologous Jets from An Emerging Flux
• Extended Calculations of Spectroscopic Data: Energy Levels, Lifetimes and Transition rates for O-like ions from Cr XVII to Zn XXIII
• Energy Levels, Lifetimes and Transition rates for P-like ions from Cr X to Zn XVI from large-scale Relativistic Multiconfiguration Calculations
• Spectroscopy of very hot plasma in non-flaring parts of a solar limb active region: spatial and temporal properties
• Benchmarking Atomic Data for Astrophysics: Be-like Ions between B II and Ne VII
• Extreme Ultraviolet Late Phase of Solar Flares
• Extremely Large Extreme-ultraviolet Late Phase Powered by Intense Early Heating in a Non-eruptive Solar Flare
• Extreme-ultraviolet Late Phase Caused by Magnetic Reconnection over Quadrupolar Magnetic Configuration in a Solar Flare
• Extreme-ultraviolet Late Phase in Homologous Solar Flares from a Complex Active Region