What are the solar astrolabe observations of the sun measuring?
Abstract
The observations of solar diameter rank with those of the solar flux and of sunspots as the ones that can and have to be made continuously to provide a better physical understanding of the Sun and of its effects on the planet Earth. Notwithstanding, the measurements of the solar diameter variations present severe difficulties, that ranges from the technical apparatus to the atmosphere disturbances. Since 1975 the remarkable measuring capabilities of the astrolabe have worldwide been put into service for this kind of observations. Although the comparison of the first published results remained, at its best, inconclusive, due to the differences of epoch, effective wavelength, and data treatment, recent results point out towards a much more coherent outcome. Such coherence owes much to the achieved unification and interchange of methods among the R2S3 (Réseau de Suivi au Sol du Rayon Solaire) group. Here we present the first direct comparison between the results obtained by solar astrolabes, namely those of Rio de Janeiro, Calern and Tubitak, thus spanning completely different conditions of observation and atmospheric regimens. The semi-diameter results are referred to the year of 2001 and the three series are shown to be outstandingly coincident. A high degree polynomial fit applied to the series presents statistical likehood better than 99%. The sense and amplitude agree with the sunspots count, while apparently in anti-phase with the solar radio flux.
- Publication:
-
Bulletin of the Astronomical Society of Brazil
- Pub Date:
- August 2003
- Bibcode:
- 2003BASBr..23...25P