Long-term hemispheric variation of the flare index

Abstract

The long-term hemispheric variation of the flare index is investigated. It is found that, (1) the phase difference of the flare index between the northern and southern hemispheres is about 6-7 months, which is near the time delay between flare activity and sunspot activity; (2) both the dominant and phase-leading hemisphere of the flare index is the northern hemisphere in the considered time interval, implying that the hemispheric asynchrony of solar activity has a close connection with the N-S asymmetry of solar activity. © 2013 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd.