Detection and characterization of high frequency and high wavenumber solar oscillations. Doctoral thesis

Technical Report · Mon Jun 01 04:00:00 EDT 1992

OSTI ID:6236634

Fernandes, D N

Doppler shift measurements of the Na D1 absorption line have revealed solar oscillations in a new regime of frequency and wavenumber. Oscillations of vertical velocities in the temperature minimum and low chromosphere of the Sun are observed with frequencies ranging up to 9.5 mHz. There is no evidence for chromospheric modes of 3 minute period. This indicates that the chromosphere does not form a good cavity for acoustic waves. The fundamental-modes appear with wavenumbers up to 5.57/Mn (equivalent spherical harmonic degree, 3877). The frequencies lie below the predicted values at wavenumbers above 1/Mn. The values are in agreement with previous measurements that exist for wavenumbers up to 2.67/Mn. Spatial maps of velocity power show that high wavenumber oscillations are suppressed in active regions. The shape of the power depression indicates that wave motion is affected in the layer of atmosphere where the measurement is made. The f-modes are suppressed in the same way as p-modes, indicating that the mechanism for wave suppression affects velocity fluctuations. Mode frequencies are not affected by the magnetic fields by more than 50 microHz, the precision of the measurement. Fluctuations in solar activity are of interest to researchers in communications and environmental/atmospheric science.

• Research Organization: Stanford Univ., CA (United States). Dept. of Physics
• OSTI ID: 6236634
• Report Number(s): AD-A-263028/3/XAB; CNN: N00014-89-J-1024
• Country of Publication: United States
• Language: English

Related Subjects

661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION SPECTRA
ATMOSPHERES
CHROMOSPHERE
DISTRIBUTION
DOPPLER EFFECT
ENERGY
ENERGY SOURCES
MAGNETIC FIELDS
MAGNETOMETERS
MAPS
MEASURING INSTRUMENTS
OSCILLATIONS
RENEWABLE ENERGY SOURCES
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR ENERGY
SPATIAL DISTRIBUTION
SPECTRA
TEMPERATURE DEPENDENCE
TEMPERATURE MEASUREMENT
WAVELENGTHS
ZEEMAN EFFECT