The relationship between solar flares and solar sector boundaries

A superposed epoch analysis of 1964–1970 solar flares shows a marked increase in flare occurrence within a day (13° of longitude) of (- +) solar sector boundaries as well as a local minimum in flare occurrence near (+ -)sector boundaries. This preference for (- +) boundaries is more noticeable for northern hemisphere flares, where these polarities match the Hale polarity law, but is not reversed in the south. Plage regions do not show such a preference.