Some properties of the latitude brightness distributions in the K and F coronae according to SOHO/LASCO data

Abstract

We have obtained continuous latitude distributions of the K and F corona brightnesses at various distances for the first time, using both the Hayes—Vourlidas—Howard method and our own recently proposed, simple technique for separating the emission of the K and F coronas. Data from the LASCO C2 and C3 coronagraphs are analyzed. Variations of the angular size of the brightness distribution of the F corona with latitude and distance are estimated, as well as the ratio of the maximum F-corona brightness to the F-corona brightness at the pole. The variations in the F-corona brightness at large distances ( R = 25 R _⊙, where R _⊙ is the solar radius) are studied on various time scales—a month, a year, and 11 years (the solar cycle). The latitude distribution of the F-corona brightness varies most appreciably over a year, and only weakly over one solar revolution and one solar-activity cycle (as considered on a fixed day of the year).