University of Minnesota
School of Physics & Astronomy

MN Institute for Astrophysics Colloquium

Friday, April 7th 2017
Speaker: Today's MIfA colloquium has been cancelled.

During solar and stellar flares, the majority of the radiated energy from the lower atmosphere escapes as white-light continuum emission in the near- ultraviolet and optical wavelength regimes. The spectral energy distribution of the white-light emission is important for assessing biomarkers in planetary atmospheres around M dwarfs and for constraining models of heating at the highest densities in flares. In this talk, I will discuss the properties of solar flares gleaned from recent IRIS data and review recent observations of M dwarf flares, including the hottest and most energetic that has been observed to date. Spectral observations and radiative-hydrodynamic modeling suggest that the white-light continuum and the chromospheric line flux in solar and stellar flares originate over two flaring layers in the lower-to-mid chromosphere. However, the fluxes of accelerated particles that are necessary to reproduce the observations are so high that the propagation of the particles to the lower atmosphere may be affected by beam instabilities. I will present our new prescription for modeling the electric pressure broadening in flare spectra, which will help resolve the problem of how the highest densities in the stellar atmosphere are heated during flares. Finally, I will speculate on aspects of habitability in the recently discovered planetary systems around the flare stars Proxima Centauri and TRAPPIST-1.

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