Observations and analysis of solar flares using H. cap alpha. spectral profiles

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1984

OSTI ID:6249397

Gunkler, T A

This dissertation approaches the chromospheric flare problem in three steps: analysis of an observed flare using existing empirical models; development of new physical models of H..cap alpha..; and analysis of another observed flare using these physical models. First, the flare of 1980 May 7 is analyzed using H..cap alpha.. spectral profiles from Sacramento Peak Observatory and cotemporal X-ray observations from the Solar Maximum Mission spacecraft. Through comparison of the observed profiles with the empirical H..cap alpha.. profiles, it is shown that chromospheric evaporation takes place concurrently with enhancement of the overlying coronal density. During the impulsive phase, it is suggested that evaporation is driven by flare-accelerated electrons. During the thermal phase, it can only be driven by thermal conduction. Next, physical models of H..cap alpha.. spectral profiles are calculated for a grid of model flare chromospheres, in both the hydrostatic and impulsive approximation. It is shown that only high fluxes of nonthermal electrons produce broad, nonGaussian profile wings, and that only high values of the coronal pressure can remove the central reversal of the profiles. Enhanced thermal conduction alone cannot account for enhanced H..cap alpha.. emission. Finally, the flare of 1980 June 24 is analyzed, showing that nonthermal electrons were accelerated bidirectionally within coronal loops and injected into the chromosphere at the loop footprints.

• Research Organization: California Univ., San Diego (USA)
• OSTI ID: 6249397
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
CHROMOSPHERE
DATA
ELECTRONS
ELEMENTARY PARTICLES
ELEMENTS
EXPERIMENTAL DATA
FERMIONS
HYDROGEN
INFORMATION
LEPTONS
MATHEMATICAL MODELS
NONMETALS
NUMERICAL DATA
PARTICLE KINEMATICS
RADIATIONS
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR ELECTRONS
SOLAR FLARES
SOLAR PARTICLES
SOLAR RADIATION
SPECTRA
STELLAR RADIATION
X-RAY SPECTRA