Carrington phase against year for the HSB at central meridian over Cycles 21–24 (top left to bottom right) in the northern hemisphere. The HSBs which had at least one RHESSI flare occurring nearby (within ±25° longitude) are coloured instead of grey, based upon the polarity change, either (+, −) red and (−, +) blue. Also shown are the observed active longitude positions (pink squares) adapted from Gyenge et al. (2016).