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

Journal Article · Fri Feb 10 00:00:00 EST 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/836/1/12· OSTI ID:22663876

Kowalski, Adam F. ^[1]; Allred, Joel C.; Daw, Adrian ^[2]; Cauzzi, Gianna ^[3]; Carlsson, Mats ^[4]

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1. Department of Astrophysical and Planetary Sciences, University of Colorado Boulder, 2000 Colorado Ave, Boulder, CO 80305 (United States)
2. NASA/Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States)
3. INAF-Osservatorio Astrofisico di Arcetri, I-50125 Firenze (Italy)
4. Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, NO-0315 Oslo (Norway)

The 2014 March 29 X1 solar flare (SOL20140329T17:48) produced bright continuum emission in the far- and near-ultraviolet (NUV) and highly asymmetric chromospheric emission lines, providing long-sought constraints on the heating mechanisms of the lower atmosphere in solar flares. We analyze the continuum and emission line data from the Interface Region Imaging Spectrograph (IRIS) of the brightest flaring magnetic footpoints in this flare. We compare the NUV spectra of the brightest pixels to new radiative-hydrodynamic predictions calculated with the RADYN code using constraints on a nonthermal electron beam inferred from the collisional thick-target modeling of hard X-ray data from Reuven Ramaty High Energy Solar Spectroscopic Imager . We show that the atmospheric response to a high beam flux density satisfactorily achieves the observed continuum brightness in the NUV. The NUV continuum emission in this flare is consistent with hydrogen (Balmer) recombination radiation that originates from low optical depth in a dense chromospheric condensation and from the stationary beam-heated layers just below the condensation. A model producing two flaring regions (a condensation and stationary layers) in the lower atmosphere is also consistent with the asymmetric Fe ii chromospheric emission line profiles observed in the impulsive phase.

• OSTI ID: 22663876
• Journal Information: Astrophysical Journal, Vol. 836, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ASYMMETRY
ATMOSPHERES
COMPARATIVE EVALUATIONS
COSMIC ELECTRONS
ELECTRON BEAMS
EMISSION
FLUX DENSITY
FORECASTING
HARD X RADIATION
HEATING
HYDRODYNAMICS
HYDROGEN
LAYERS
LIMITING VALUES
RADIANT HEAT TRANSFER
RECOMBINATION
SIMULATION
SOLAR FLARES
SUN
ULTRAVIOLET RADIATION