Photometry of a Solar Flare

Orren C. Mohler
1947 Publications of the Astronomical Society of the Pacific  
The McMath-Hulbert Observatory has in progress a program of measurement of the brightness of solar flares. The measures are made on spectroheliograms obtained with the 50foot tower telescope of the McMath-Hulbert Observatory. All images are recorded on 35 .mm motion picture film, Eastman emulsion 0-405-05-01. Each series of photographs has been standardized with an optical wedge, using the center of the sun as a light source. Particularly interesting results have been obtained for the rate of
more » ... crease in brightness and .rate of fading of the flare phenomena. The following data concerning one of the flares on December 11, 1946, will serve as an example of the information we are obtaining. The detailed results for the twelve flares that have so far been measured will be published in full later. A brilliant flare appeared in the spot group at position : meridian distance 70° east; latitude 7° south. The disturbance was first noted visually on December 11, 1946, at 16 h 41 m 32 s U.T. The measurement of the brightness of an area of 20 square seconds can be represented in the following way : Preflare : log 10 1/h = -( 1.22 X 10+1 + 0.22, 0 ^ t ^ 480 s . Flare stage : log 10 1/h = +(4.86 X 10" 3 )t -2.2, 480 s < t ^ 549 s . Fading stage : log 10 1/h = -(3.20 X 10-4 )t + 0.69, 549 s ^ t ^ 1697 s .
doi:10.1086/125965 fatcat:jk5i3i2xvzblnia7vjrwk7ahiu