First Detection of Solar Flare Emission in Middle-Ultraviolet Balmer Continuum

Abstract

We present the first detection of solar flare emission at middle-ultraviolet wavelengths around 2000 A by the channel 2 of the Large-Yield RAdiometer (LYRA) onboard the PROBA2 mission. The flare (SOL20170906) was also observed in the channel 1 of LYRA centered at the H I Lyman-α line at 1216 A, showing a clear non-thermal profile in both channels. The flare radiation in channel 2 is consistent with the hydrogen Balmer continuum emission produced by an optically thin chromospheric slab heated up to 10000 K. Simultaneous observations in channels 1 and 2 allow the separation of the line emission (primarily from the Lyman-α line) from the Balmer continuum emission. Together with the recent detection of the Balmer continuum emission in the near-ultraviolet by IRIS, the LYRA observations strengthen the interpretation of broadband flare emission as the hydrogen recombination continua originating in the chromosphere.

References in corpus (18)

• The Interface Region Imaging Spectrograph (IRIS)
• Global Energetics of Thirty-Eight Large Solar Eruptive Events
• Sun-as-a-star Observation of White-Light Flares
• The Radiated Energy Budget of Chromospheric Plasma in a Major Solar Flare Deduced From Multi-Wavelength Observations
• Continuum Enhancements in the Ultraviolet, the Visible and the Infrared during the X1 flare on 2014 March 29
• On-Orbit Degradation of Solar Instruments
• 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
• The LYRA Instrument Onboard PROBA2: Description and In-Flight Performance
• Detection of 3-Minute Oscillations in Full-Disk Ly$\alpha$ Emission During A Solar Flare
• On the nature of off-limb flare continuum sources detected by SDO/HMI
• Observations of a solar flare and filament eruption in Lyman alpha and X-rays
• Sun-as-a-Star Observation of Flares in Lyman α by the PROBA2/LYRA radiometer
• The Anomalous Temporal Behaviour of Broadband Ly$\alpha$ Emission During Solar Flares From SDO/EVE
• Understanding the HMI pseudocontinuum in white-light solar flares
• On the origin of the flare emission in IRIS' SJI 2832 filter: Balmer continuum or spectral lines?
• New Observations of Balmer Continuum Flux in Solar Flares, Instrument Description and First Results
• Automatic detection of white-light flare kernels in SDO/HMI intensitygrams

Cited by in corpus (15)

• Extending Optical Flare Models to the UV: Results from Comparing of TESS and GALEX Flare Observations For M Dwarfs
• Detection of flare multi-periodic pulsations in mid-ultraviolet Balmer continuum, Ly-alpha, hard X-ray, and radio emissions simultaneously
• Quasi-periodic pulsations of gamma-ray emissions from a solar flare on 2017 September 06
• Quasi-periodic pulsation detected in Lyman-alpha emission during solar flares
• Bridging High-Density, Electron Beam Coronal Transport and Deep Chromospheric Heating in Stellar Flares
• Solar Irradiance Variability Due To Solar Flares Observed in Lyman-alpha Emission
• Simultaneous Observations of Chromospheric Evaporation and Condensation during a C-class Flare
• The 2017 September 6 Flare: Radio Bursts and Pulsations in the 22-5000 MHz Range and Associated Phenomena
• Unveiling Spatiotemporal Properties of the Quasi-periodic Pulsations in the Balmer Continuum at 3600 Å in an X-class Solar White-light Flare
• The Lyman-alpha Emission in Solar Flares. I. a Statistical Study on Its Relationship with the 1--8 Å Soft X-ray Emission
• Flare heating of the chromosphere: Observations of flare continuum from GREGOR and IRIS
• Global energetics of solar powerful events on 6 September 2017
• The Lyman-$\alpha$ Emission in a C1.4 Solar Flare Observed by the Extreme Ultraviolet Imager aboard Solar Orbiter
• Predicted white-light solar flare emission from the F-CHROMA grid of models
• Non-Linear Solar EUV-Driven Sodium Release from the Lunar Surface: A Contrast to the Linear PSD Model