Extreme-ultraviolet Late Phase in Homologous Solar Flares from a Complex Active Region

Abstract

Recent observations in extreme-ultraviolet (EUV) wavelengths reveal a new late phase in some solar flares, which is seen as a second peak in warm coronal emissions ($\sim 3$ MK) several tens of minutes to a few hours after the soft X-ray (SXR) peak. The origin of the EUV late phase (ELP) is explained by either a long-lasting cooling process in the long ELP loops, or a delayed energy ejection into the ELP loops well after the main flare heating. Using the observations with the \emph{Solar Dynamics Observatory} (\emph{SDO}), we investigate the production of the ELP in six homologous flares (F1--F6) originating from a complex active region (AR) NOAA 11283, with an emphasis on the emission characteristics of the flares. It is found that the main production mechanism of the ELP changes from additional heating in flare F1 to long-lasting cooling in flares F3--F6, with both mechanisms playing a role in flare F2. The transition is evidenced by an abrupt decrease of the time lag of the ELP peak, and the long-lasting cooling process in the majority of the flares is validated by a positive correlation between the flare ribbon fluence and the ELP peak intensity. We attribute the change in ELP production mechanism to an enhancement of the envelope magnetic field above the AR, which facilitates a more prompt and energetic heating of the ELP loops. In addition, the last and the only confined flare F6 exhibits an extremely large ELP. The different emission pattern revealed in this flare may reflect a different energy partitioning inside the ELP loops, which is due to a different magnetic reconnection process.

arXiv comment26 pages, 12 figures, 3 tables, accepted for publication in ApJ

References in corpus (29)

• A Model for Solar Coronal Mass Ejections
• Torus instability
• An Observational Overview of Solar Flares
• Highly Efficient Modeling of Dynamic Coronal Loops
• Thermal Diagnostics with the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory: A Validated Method for Differential Emission Measure Inversions
• Hot Spine Loops and the Nature of a Late-Phase Solar Flare
• Imaging and Spectroscopic Observations of a Filament Channel and the Implications for the Nature of Counter-streamings
• Enthalpy-based Thermal Evolution of Loops: II. Improvements to the Model
• Chirality and Magnetic Configurations of Solar Filaments
• Formation and Eruption of an Active Region Sigmoid: I. Study by Nonlinear Force-Free Field Modeling
• Multiwavelength observations of a partially eruptive filament on 2011 September 8
• Inference of Heating Properties from "Hot" Non-flaring Plasmas in Active Region Cores I. Single Nanoflares
• Flux rope, hyperbolic flux tube, and late EUV phases in a non-eruptive circular-ribbon flare
• On the origin of the Extreme-Ultraviolet late phase of solar flares
• Three-dimensional Magnetic Restructuring in Two Homologous Solar Flares in the Seismically Active NOAA AR 11283
• Evolution of the Toroidal Flux of CME Flux Ropes during Eruption
• Production of the Extreme-Ultraviolet Late Phase of an X Class Flare in a Three-Stage Magnetic Reconnection Process
• The Nature of CME-Flare Associated Coronal Dimming
• Is flux rope a necessary condition for the progenitor of coronal mass ejections?
• On the Nature of the Extreme-Ultraviolet Late Phase of Solar Flares
• Thermodynamic Spectrum of Solar Flares Based on SDO/EVE Observations: Techniques and Statistical Results
• Extreme Ultraviolet Late Phase of Solar Flares
• Comparison of Emission Properties of two Homologous Flares in AR 11283
• Extremely Large Extreme-ultraviolet Late Phase Powered by Intense Early Heating in a Non-eruptive Solar Flare
• The Neupert Effect of Flare UltraViolet and Soft X-ray Emissions
• The Response of the Lyman-Alpha Line in Different Flare Heating Models
• Probing the Production of Extreme-ultraviolet Late-Phase Solar Flares by Using the Model Enthalpy-Based Thermal Evolution of Loops
• Extreme-ultraviolet Late Phase Caused by Magnetic Reconnection over Quadrupolar Magnetic Configuration in a Solar Flare
• Gradual Magnetic Evolution of Sunspot Structure and Filament-Corona Dynamics Associated with the X1.8 Flare in AR 11283