Análise de observações do diâmetro no contexto da atividade solar

Abstract

From 1997 to 2003 the CCD Solar Astrolabe of the Observatório Nacional in Rio de Janeiro made more than 20,000 observations of the Solar Semidiameter. The experimental data from1998 to 2001 had been obtained in two independent previous works, by the corrections of the systematic effects on the raw observational results. In the present work similar corrections for the observational results of 2002 and 2003 were determined. Aiming at the robustness of the corrections, the measurements of each year have been considered separately, as well as the series of observational data as taken at east or west from the local meridian were separately considered. Initially, for each annual series a statistical approach was used, justified by the amount of data. The values to east and west have been corrected in function of their mean quadratic offset to the local trend averages, therefore without modifying the measured variations. Finally, the values have been corrected of the bias, using coefficients obtained from the correlation between the parameters and the observational measures. The series of 16.523 coherent data of the variation of the Solar Semidiameter, between 1998 and 2003, allowed the detailed comparison with series of pointers of the solar activity: Flare Index, Total Irradiance, Integrated Magnetic Field, Sunspot Number and 10.7cm Radio Flux. The hypothesis of variation of the Semidiameter tied to the solar activity, otherwise being its estimator, was examined through the correlations between the different pairs of pointers. The correlations have been calculated at continuous spacing of the series of values, from the data annual division until the monthly division. Strong correlations between some pairs were obtained, and interpreted as strong physical interaction between them. For the pair Solar Semidiameter and Irradiance the mode of the phase for maximum correlation was calculated for two distinct cases: either for the complete series of data, or leaving off the data relative to the epochs of the two summits of the solar activity cycle. The comparison shows that the Solar Semidiameter responds closely to variations of Irradiance in the conditions where the peaks of activity are considered inversely, it precedes the variations of Irradiance, by at least one hundred days, when the peak values are discarded, thus indicating the existence of two distinct regimes. We also studied how the Solar Semidiameter varies throughout its latitudes. It was noted that each band of latitude has a different response, even so there is a global variation in time. It was also determined the solar latitude bands that exhibit small modules for the Solar Semidiameter variation and those bands where the variation modules are much stronger.