Helium resonance lines in the flare of 15 June, 1973

Technical Report · Mon Jun 25 04:00:00 EDT 1990

OSTI ID:6515830

Porter, J G; Gebbie, K B; November, L J

Time sequence of He l and He ll resonance line intensities at several sites within the flare of 15 June, 1973 are derived from observations obtained with the Naval Research Laboratory's Slitless Spectroheliograph on Skylab. The data are compared with predictions in six model flare atmospheres based on two values for the heating rate and three for the flux of photoionizing coronal X-rays and EUV. A peak ionizing flux more than 1000 times that in the quiet Sun is indicated. For most conditions in flare kernels the He ll L alpha and L beta lines are found to be formed by collisional excitation, thereby contributing to the local cooling of the plasma at temperatures above 60000 K. Emission in the higher Lyman lines is generally the result of a mixture of collisional excitation at these temperatures and photoionization and recombination at temperatures near 25000 K. We discuss implications for the common practice of deriving stellar coronal fluxes from He ll 1640 A fluxes assuming dominance of the recombination mechanism.

• Research Organization: Air Force Geophysics Lab., Hanscom AFB, MA (USA)
• OSTI ID: 6515830
• Report Number(s): AD-A-225185/8/XAB; GL-TR--90-0162
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
COLLISIONS
COMPARATIVE EVALUATIONS
COOLING
DISPERSIONS
ELECTROMAGNETIC RADIATION
ELEMENTS
ENERGY-LEVEL TRANSITIONS
EXCITATION
FLUIDS
GASES
HEATING
HELIUM
IONIZATION
IONIZING RADIATIONS
LYMAN LINES
MAIN SEQUENCE STARS
MIXTURES
NONMETALS
PHOTOIONIZATION
RADIATION FLUX
RADIATIONS
RARE GASES
RECOMBINATION
RESONANCE
SOLAR ACTIVITY
SOLAR CORONA
SOLAR FLARES
SPECTRA
STARS
STELLAR ATMOSPHERES
STELLAR CORONAE
SUN
X RADIATION