An observational and theoretical investigation of stellar flares

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:6599126

Hawley, S L

Multi-wavelength observations of a giant flare on the star AD Leo were obtained with the 2.1m and 0.9m telescopes at McDonald Observatory and the International Ultraviolet Explorer satellite. A self-consistent theoretical model was developed to investigate the effects of chromospheric heating by thermal conduction and soft x-ray irradiation from a flare heated corona. Assuming a one-dimensional coronal loop geometry, atmospheres were produced for overlying coronal temperatures of 8, 10, 15, and 20 million degrees Kelvin. The atmospheres satisfy the equations of hydrostatic equilibrium, steady state energy balance, and statistical equilibrium and radiative transfer in many optically thick transitions of hydrogen, ionized calcium and ionized magnesium. A second theoretical model was then developed to predict the temporal evolution of the coronal temperature under the influence of a time varying flare heating rate. Combining the models, the chromospheric emission model predictions in the hydrogen Balmer lines, Ca II K, Mg II h + k and the optical continuum were compared to the observations, with the result that much of the gradual phase flare emission could be produced by the x-ray and conductive heated atmospheres. Soft x-ray and conductive heating of the chromosphere is a natural consequence of the coronal temperatures that have been observed during the gradual phase of flares on the sun and on M dwarf stars. The improved flare observations and quantitative flare models presented here show that these heating mechanisms can produce atmospheres whose emission matches many of the observed stellar flare features.

• Research Organization: Texas Univ., Austin, TX (USA)
• OSTI ID: 6599126
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
BALMER LINES
DWARF STARS
ELECTROMAGNETIC RADIATION
EMISSION SPECTRA
HEATING
IONIZING RADIATIONS
MAIN SEQUENCE STARS
MATHEMATICAL MODELS
RADIATION TRANSPORT
RADIATIONS
SELF-CONSISTENT FIELD
SOFT X RADIATION
SPECTRA
STARS
STELLAR ACTIVITY
STELLAR ATMOSPHERES
STELLAR FLARES
SUN
TEMPERATURE GRADIENTS
X RADIATION