Large-Scale Periodic Solar Velocities: An Observational Study.
Abstract
Observations of large-scale solar velocities have been made using the mean field telescope and Babcock magnetograph of the Stanford Solar Observatory. Observations were made in the magnetically insensitive iron line at 5124 A, with light from the center (limb) of the disk right (left) circularly polarized, so that the magnetograph measures the difference in wavelength between center and limb. Computer calculations are made of the wavelength difference produced by global pulsations for spherical harmonics up to second order. Computations are also made of the signal produced by displacing the solar image relative to polarizing optics or diffraction grating. Such displacements are the probable source of slow drifts in the observed signal. Individual observations clearly show the five-minute oscillations. From power spectra, the amplitude is 2.0 meters/second, and the period is 312.9 + or - 0.9 seconds. The amplitude gives evidence for a horizontal wavelength greater than 20000 kilometers, and the period is larger than reported for smaller apertures. Six months of almost daily observations have been examined for changes in oscillatory power or period that might be associated with large-scale coronal and solar wind structures as identified by solar sector boundaries, the amplitude of the mean magnetic field, or the C9 index. No evidence for large-scale organization of the oscillations has been found.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1977
- Accession Number
- ADA040653
Entities
People
- Phil Howard Dittmer
Organizations
- Stanford University