Atmospheric Variations

Abstract

FROM the results of recent researches solar prominences seem to be playing a most important part, not only in the mechanism of the solar atmosphere, but in the variations of our own. Any investigation, therefore, that gives us new ideas or corroborates the old is most useful and valuable. In a previous number of this Journal (vol. lxvii. p. 569, April) an account wTas given of the results obtained from a research on the distribution of solar prominences as regards latitude. The prominence circulation thus disclosed that there was practically a law at work which the centres of prominence action followed, and this law, deduced from observations extending over the longest period available (1872–1901), was found to be in good agreement with that first suggested by Prof. Ricco An 1891 (Mem. d. Soc. degli Spettr., vol. xx. p. 135). Prof. Bigelow has also been studying the question of prominence, facula and spot circulation, and in a recent number of the Monthly Weather Review (vol. xxxi. No. 1, p. 9) has stated his results. The method he adopted was somewhat different from the one first mentioned above, for the prominence circulation determined by him has been deduced by finding the mean variation of the prominence distribution resulting from coupling up together the values for those years which he considers are similar in relation to the eleven-year sun-spot cycle. Anyone familiar with this cycle knows the difficulty this involves, because it is only the mean length of the sun-spot period that is eleven years. Further, the. epochs of maxima do not follow those of the minima at constant intervals, but vary from a little more than three to five years. In spite, however, of these probable sources of error, Prof. Bigelow deduces a circulation not very different from the one mentioned above, so that all the three computations and deductions show that there is a very definite movement in latitude and change in percentage frequency of occurrence from year to year.