Impulsive energy release and non-thermal emission in a confined M4.0 flare triggered by rapidly evolving magnetic structures

Abstract

We present observations of a confined M4.0 flare from NOAA 11302 on 2011 September 26. Observations at high temporal, spatial, and spectral resolution from Solar Dynamics Observatory, Reuven Ramaty High Energy Solar Spectroscopic Imager, and Nobeyama Radioheliograph enabled us to explore the possible triggering and energy release processes of this flare despite its very impulsive behavior and compact morphology. The flare light curves exhibit an abrupt rise of non-thermal emission with co-temporal hard X-ray (HXR) and microwave (MW) bursts that peaked instantly without any precursor emission. This stage was associated with HXR emission up to 200 keV that followed a power law with photon spectral index ($\delta$) $\sim$3. Another non-thermal peak, observed 32 s later, was more pronounced in the MW flux than the HXR profiles. Dual peaked structure in the MW and HXR light curves suggest a two-step magnetic reconnection process. Extreme ultraviolet (EUV) images exhibit a sequential evolution of the inner and outer core regions of magnetic loop system while the overlying loop configuration remained unaltered. Combined observations in HXR, (E)UV, and H$\alpha$ provide support for flare models involving interaction of coronal loops. The magnetograms obtained from Helioseismic and Magnetic Imager (HMI) reveal the emergence of magnetic flux which started $\sim$5 hr before the flare. However, the more crucial changes in the photospheric magnetic flux occurred about 1 minute prior to the flare onset with opposite polarity magnetic transients appearing at the early flare location within the inner core region. The spectral, temporal, and spatial properties of magnetic transients suggest that the sudden changes in the small-scale magnetic field have likely triggered the flare by destabilizing the highly sheared pre-flare magnetic configuration.

arXiv comment18 pages, Accepted for publication in ApJ

References in corpus (12)

• Confined and ejective eruptions of kink-unstable flux ropes
• Ideal kink instability of a magnetic loop equilibrium
• Magnetic Field Structures Triggering Solar Flares and Coronal Mass Ejections
• Combined STEREO/RHESSI study of CME acceleration and particle acceleration in solar flares
• A Comparative Study Between Eruptive X-class Flares Associated with Coronal Mass Ejections and Confined X-class Flares
• The spectral evolution of impulsive solar X-ray flares
• Magnetic Reconnection During the Two-Phase Evolution of a Solar Eruptive Flare
• Global Twist of Sunspot Magnetic Fields Obtained from High Resolution Vector Magnetograms
• Pre-flare activity and magnetic reconnection during the evolutionary stages of energy release in a solar eruptive flare
• Velocity and Magnetic Transients Driven by the X2.2 White-Light Flare of 2011 February 15 in NOAA 11158
• Plasma heating in the very early phase of solar flares
• Magnetic Non-Potentiality of Solar Active Regions and Peak X-Ray Flux of the Associated Flares

Cited by in corpus (18)

• High-Mass Star and Massive Cluster Formation in the Milky Way
• Helical Kink Instability in a Confined Solar Eruption
• Solar X-ray Monitor On Board the Chandrayaan-2 Orbiter: In-flight Performance and Science Prospects
• Large-scale contraction and subsequent disruption of coronal loops during various phases of the M6.2 flare associated with the confined flux rope eruption
• Development of a Confined Circular-cum-parallel Ribbon Flare and Associated Pre-flare Activity
• Eruptive-Impulsive Homologous M-class Flares Associated with Double-Decker Flux Rope Configuration in Mini-Sigmoid of NOAA 12673
• Two-stage energy release process of a confined flare with double HXR peaks
• Generalisation of the Magnetic Field Configuration of typical and atypical Confined Flares
• Observations of a prominence eruption and loop contraction
• Observational and model analysis of a two-ribbon flare possibly induced by a neighbouring blowout jet
• Multiwavelength Signatures of Episodic Null Point Reconnection in a Quadrupolar Magnetic Configuration and the Cause of Failed Flux Rope Eruption
• Energy Partition in Four Confined Circular-Ribbon Flares
• Investigation of two coronal mass ejections from circular ribbon source region: Origin, Sun-Earth propagation and Geo-effectiveness
• A Transient Coronal Sigmoid in Active Region NOAA 11909: Build-up Phase, M-class Eruptive Flare, and Associated Fast Coronal Mass Ejection
• Two-stage evolution of an extended C-class eruptive flaring activity from sigmoid active region NOAA 12734: SDO and Udaipur-CALLISTO observations
• Observation of 2011-02-15 X2.2 flare in Hard X-ray and Microwave
• Homologous compact major blowout-eruption solar flares and their production of broad CMEs
• Aditya-L1 and SDO Observations of a Confined X-Class Flare with an EUV Late Phase: Thermal and Nonthermal Emission, Magnetic Topology, and Flux Rope Confinement