Optical Spectral Observations of a Flickering White-Light Kernel in a C1 Solar Flare

Abstract

We analyze optical spectra of a two-ribbon, long duration C1.1 flare that occurred on 18 Aug 2011 within AR 11271 (SOL2011-08-18T15:15). The impulsive phase of the flare was observed with a comprehensive set of space-borne and ground-based instruments, which provide a range of unique diagnostics of the lower flaring atmosphere. Here we report the detection of enhanced continuum emission, observed in low-resolution spectra from 3600 Å to 4550 Å acquired with the Horizontal Spectrograph at the Dunn Solar Telescope. A small, $\le$0''.5 ($10^{15}$ cm${}^2$) penumbral/umbral kernel brightens repeatedly in the optical continuum and chromospheric emission lines, similar to the temporal characteristics of the hard X-ray variation as detected by the Gamma-ray Burst Monitor (GBM) on the Fermi spacecraft. Radiative-hydrodynamic flare models that employ a nonthermal electron beam energy flux high enough to produce the optical contrast in our flare spectra would predict a large Balmer jump in emission, indicative of hydrogen recombination radiation from the upper flare chromosphere. However, we find no evidence of such a Balmer jump in the bluemost spectral region of the continuum excess. Just redward of the expected Balmer jump, we find evidence of a "blue continuum bump" in the excess emission which may be indicative of the merging of the higher order Balmer lines. The large number of observational constraints provides a springboard for modeling the blue/optical emission for this particular flare with radiative-hydrodynamic codes, which are necessary to understand the opacity effects for the continuum and emission line radiation at these wavelengths.

arXiv comment54 pages, 13 figures, accepted for publication in the Astrophysical Journal

References in corpus (23)

• The Fermi Gamma-Ray Burst Monitor
• Global Energetics of Thirty-Eight Large Solar Eruptive Events
• Impulsive phase flare energy transport by large-scale Alfven waves and the electron acceleration problem
• Radiative Hydrodynamic Models of the Optical and Ultraviolet Emission from Solar Flares
• Does a Non-Magnetic Solar Chromosphere Exist?
• Time-Resolved Properties and Global Trends in dMe Flares from Simultaneous Photometry and Spectra
• Stochastic Acceleration of Electrons and Protons. I. Acceleration by Parallel Propagating Waves
• Sun-as-a-star Observation of White-Light Flares
• Are Coronae of Magnetically Active Stars Heated by Flares? II. EUV and X-Ray Flare Statistics and the Differential Emission Measure Distribution
• ROSA: a high cadence, synchronized multi-camera solar imaging system
• Do all Flares have White Light Emission?
• Flare Heating in Stellar Coronae
• Propagation of Alfvénic Waves From Corona to Chromosphere and Consequences for Solar Flares
• Multiwavelength observations of a giant flare on CN Leonis I. The chromosphere as seen in the optical spectra
• Hydrogen Balmer Continuum in Solar Flares Detected by the Interface Region Imaging Spectrograph (IRIS)
• Physical Properties of White-Light Sources in the 2011 Feb 15 Solar Flare
• From Radio to X-ray: The Quiescent Atmosphere of the dMe Flare Star EV Lacertae
• Fine structure of flare ribbons and evolution of electric currents
• High-Cadence and High-Resolution Halpha Imaging Spectroscopy of a Circular Flare's Remote Ribbon with IBIS
• Observations and modelling of a large optical flare on AT Microscopii
• Emission Height and Temperature Distribution of White-Light Emission Observed by Hinode/SOT from the 2012 January 27 X-class Solar Flare
• High time resolution observations of solar H-alpha flares - II. Search for signatures of electron beam heating
• The Effects of Atmospheric Dispersion on High-Resolution Solar Spectroscopy

Cited by in corpus (16)

• The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares I: Modeling the Brightest NUV Footpoints in the X1 Solar Flare of 2014 March 29
• New Insights into White-Light Flare Emission from Radiative-Hydrodynamic Modeling of a Chromospheric Condensation
• Spectral signatures of chromospheric condensation in a major solar flare
• Hydrogen Balmer Line Broadening in Solar and Stellar Flares
• The Near-Ultraviolet Continuum Radiation in the Impulsive Phase of HF/GF-Type dMe Flares I: Data
• The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. II. Hydrogen Broadening Predictions for Solar Flare Observations with the Daniel K. Inouye Solar Telescope
• Spectral Evidence for Heating at Large Column Mass in Umbral Solar Flare Kernels I: IRIS NUV Spectra of the X1 Solar Flare of 2014 Oct 25
• A multi-wavelength view of magnetic flaring from PMS stars
• Observations of white-light flares in NOAA active region 11515: high occurrence rate and relationship with magnetic transients
• Time-resolved UVES observations of a stellar flare on the planet host HD 189733 during primary transit
• Bridging High-Density, Electron Beam Coronal Transport and Deep Chromospheric Heating in Stellar Flares
• Suppression of Hydrogen Emission in an X-class White-light Solar Flare
• IBIS-A: The IBIS data Archive. High resolution observations of the solar photosphere and chromosphere with contextual data
• Using Close White Dwarf + M Dwarf Stellar Pairs to Constrain the Flare Rates in Close Stellar Binaries
• The CUBES Science Case
• White-light continuum emission from a solar flare and plage