Researches on the Limb Darkening of the Sun by the Observation of Annular Eclipse

[摘要] We observed the annular eclipse of May 9th, 1948 at Rebun Island, Hokkaido. By equipping the direct solarimeter with a photo-tube at its base and with a filter having a maximum intensity at 5000Å at the entrance of the cylinder of this instrument, we observed the solar radiation by a pointing galvanometer and obtained a satisfactory and splendid eclipse curve. Before the commencement of the eclipse we obtained the coefficient of transmission p=0.8 by observation.By the eclipse curve we studied the effect of the limb darkening. The results were as follows:From radius r=0 to 0.95 on the sun's disk (the radius of the sun's disk being taken as 1) the radiative equilibrium is predominant, i.e., I(r)=I0(1-U+U√1-r2) and U=1/5, where I0 is the intensity at the sun's certre. While from r=0.95 to r=1.0 the convective equilibrium is prevalent, i.e I(r)=I0(1-r2)2(C-1)/C C=5/3.

[学科分类] 大气科学