Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-03-08
Astrophys.J. 644 (2006) 484-496
Astronomy and Astrophysics
Astrophysics
Accepted for publication in the ApJ
Scientific paper
10.1086/503314
We report on radiative hydrodynamic simulations of M dwarf stellar flares and compare the model predictions to observations of several flares. The flares were simulated by calculating the hydrodynamic response of a model M dwarf atmosphere to a beam of non-thermal electrons. Radiative backwarming through numerous soft X-ray, extreme ultraviolet, and ultraviolet transitions are also included. The equations of radiative transfer and statistical equilibrium are treated in non-LTE for many transitions of hydrogen, helium and the Ca II ion allowing the calculation of detailed line profiles and continuum radiation. Two simulations were carried out, with electron beam fluxes corresponding to moderate and strong beam heating. In both cases we find the dynamics can be naturally divided into two phases: an initial gentle phase in which hydrogen and helium radiate away much of the beam energy, and an explosive phase characterized by large hydrodynamic waves. During the initial phase, lower chromospheric material is evaporated into higher regions of the atmosphere causing many lines and continua to brighten dramatically. The He II Lya line is especially enhanced, becoming the brightest line in the flaring spectrum. The hydrogen Balmer lines also become much brighter and show very broad line widths, in agreement with observations. We compare our predicted Balmer decrements to decrements calculated for several flare observations and find the predictions to be in general agreement with the observations. During the explosive phase both condensation and evaporation waves are produced. The moderate flare simulation predicts a peak evaporation wave of 130 km/s and a condensation wave of 30 km/s. The velocity of the condensation wave matches velocities observed in several transition region lines.
Abbett William P.
Allred Joel C.
Carlsson Mats
Hawley Suzanne L.
No associations
LandOfFree
Radiative Hydrodynamic Models of Optical and Ultraviolet Emission from M Dwarf Flares does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Radiative Hydrodynamic Models of Optical and Ultraviolet Emission from M Dwarf Flares, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radiative Hydrodynamic Models of Optical and Ultraviolet Emission from M Dwarf Flares will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-446499