A Measurement of the Radial Brightness Variation at the Extreme Solar Limb.
Abstract
The solar limb darkening function is obtained at 433 nm from measurements made at the total solar eclipse of 7 March 1970 at Virginia Beach, Va. Light from the waning solar crescent was monitored photoelectrically and the photomultiplier output was recorded on magnetic tape. The resulting eclipse curve is analyzed by the method of Julius which is modified in three ways to allow the use of small zones and also to minimize the effects of irregularities in the lunar limb. A criterion is developed for locating the effective zone radii in terms of the irregularities by assuming that the limb darkening function is linear over each zone. Finally, the zone widths are taken successively wider away from the limb in order to minimize the contributions of errors in the outer few zones to the calculations of inner zone intensities. With these modifications the limb darkening function is obtained over the range 0.937 to 0.99988 solar radius. A distinct limb brightening effect is found at R = 0.999 solar radius. This is shown to correspond to a thin hot layer at an optical depth of 0.05.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1978
- Bibcode:
- 1978PhDT.........5R
- Keywords:
-
- Physics: Astronomy and Astrophysics;
- Brightness;
- Limb Darkening;
- Radial Distribution;
- Solar Limb;
- Irregularities;
- Luminous Intensity;
- Solar Eclipses;
- Solar Physics