Wednesday, March 30, 2016 at 4:00pm

JILA Auditorium

Adam Kowalski, NASA/GSFC Heliophysics Science Division

"The Optical and Near-Ultraviolet Continuum Emission in Stellar Flares"

Abstract:

Flares result from the sudden reconnection and relaxation of magnetic fields in the coronae of stellar atmospheres. The highly dynamic atmospheric response produces radiation across the electromagnetic spectrum, from the radio to X-rays, on a range of timescales, from seconds to days. The optical and near-ultraviolet (white-light) continuum emission is thought to originate from high densities at T~10,000 K, which are conditions in the flare atmosphere that are not easily produced by any standard heating mechanism. In this talk, I discuss the formation of the white-light continuum emission in new 1D radiative-hydrodynamic models of dMe and solar flares. We present recent progress with high-flux nonthermal electron beams in reproducing the observed optical continuum color temperature of T~10,000 K and the Balmer jump properties in the near- ultraviolet. These high-flux electron beams produce dense, heated chromospheric condensations, which can explain the shape and strength of the continuum emission in dMe flares and the red-wing asymmetries observed in chromospheric emission lines in solar flares. Future observational and modeling directions will also be discussed.

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