Cyclic behavior of solar full‐disk activity

Abstract

In order to describe the cyclic behavior of solar full‐disk activity (the surface magnetic fields, filaments, the green Fe XIV, 5303Å corona local maxima intensities, and torsional oscillations), we propose a new concept, a “full‐disk activity cycle,” which consists of two successive normal cycles: a high‐latitude activity cycle following a low‐latitude activity cycle. When solar activity begins to progress into a full‐disk activity cycle, it latitudinally rushes to the poles, starting from middle latitudes (about 40°) at about a normal cycle minimum. At the solar poles, magnetic polarity reversal takes place on both the solar hemispheres, and opposite reversals occur on the opposite hemispheres; resultingly, the new appearing magnetic polarity at high latitudes on a hemisphere will become the leading magnetic polarity of regions at low latitudes on the same hemisphere in the following normal cycle. After the latitudinal drift of solar activity reaches the solar poles at about the maximum time of the normal cycle, solar activity begins to latitudinally migrate in a reverse direction; it moves toward the equator continually till almost arriving at the solar equator and lasting for about 1.5 normal cycles. When a full‐disk activity cycle progresses from a high‐latitude activity cycle into a low‐latitude activity cycle, the next full‐disk activity cycle begins. Two successive full‐disk activity cycles have a normal cycle overlapped in time but are spatially separated. The characteristics of full‐disk activity cycles are summarized as well. At present we do not know why a full‐disk activity cycle begins at midlatitudes; it is perhaps related with solar differential rotation. Further work is required to uncover the physical mechanisms behind the concept.