Sunspot vector magnetic fields and model umbral atmospheres

Thesis/Dissertation · Mon Jan 01 00:00:00 EST 1979

OSTI ID:6249191

Gurman, J B

The Stokes parameters provide a complete description of the polarization of electromagnetic radiation. The Stokes polarimeter of the High Altitude Observatory, which is capable of measuring all four Stokes parameters simultaneously across a spectral line profile, has been used to observe a round, unipolar sunspot in three absorption lines and the nearby continua. Observations in the weak Zeeman triplet lambda 6302.50 A are used to derive the vector magnetic field vector B across the spot. Doppler-shift measurements in the Zeeman-insensitive line Fe I lambda 5576.10 A show no significant vertical flows in the spot. Finally, Stokes profiles of the Zeeman-sensitive resonance line Na I D/sub 2/ lambda 5889.96 A are used to probe the depth variation of the magnetic field and to obtain a model atmosphere for the umbra. The weak Zeeman line measurements are in accord with the traditional view of vector B in a sunspot: The field is strongest and nearly vertical at the center of the umbra, but decreases in strength and elevation outward. The field vector does not, however, vanish at the outer edge of the spot. The field azimuth is primarily radial, but some changes are visible from day to day. A linear anticorrelation is found between the continuum intensity and the magnetic field strength. Time series observations in the umbra show significant power in the field strength and contimuum intensity at periods of (197 +- 25) seconds and (266 +- 35) seconds, respectively. A smaller, but still noteworthy, amount of power is evident in the transverse component at the (197 +- 25) second period.

• Research Organization: Colorado Univ., Boulder (USA)
• OSTI ID: 6249191
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
SUNSPOTS
MAGNETIC FIELDS
ABSORPTION SPECTRA
LTE
MATHEMATICAL MODELS
POLARIMETERS
SODIUM IONS
SOLAR ATMOSPHERE
STOKES PARAMETERS
TURBULENCE
VECTOR FIELDS
ZEEMAN EFFECT
ATMOSPHERES
CHARGED PARTICLES
EQUILIBRIUM
IONS
SOLAR ACTIVITY
SPECTRA
640104* - Astrophysics & Cosmology- Solar Phenomena