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.

A brief review on the presentation of cycle 24, the first integrated solar cycle in the new millennium

“…Helioseismology interpretation for the low level of solar activity in cycle 24 does not resolve the basic questions. The zonal flow band observed by Helioseismology and the magnetic field at the solar surface have the similar cyclic behaviour of solar full-disk activity, and the two are probably only the shadows of a more potent phenomenon occurring within the convection zone (Snodgrass, 1987;Li et al, 2008). How do the zonal flow bands trigger sunspot production, and how do the zonal flow bands emerge?…”

“…The migrating zonal flow pattern, known as the torsional oscillation, was first detected by Howard and Labonte (1980) in Doppler measurements at the solar surface carried out at the Mount Wilson Observatory; it consists of belts of slightly faster than average rotation that migrate from mid-latitudes to both the equator and poles. The migration of the zonal flow bands during the solar cycle is closely connected to the migration of the magnetic activity belt (Howe et al, 2009;Li et al, 2008). When the zonal flow bands, marching toward the equator, reaches the critical latitude of 22 degrees, sunspots of the new cycle begin to appear over the solar disk.…”

Latitude migration of solar filaments

“…Mein & Ribes (1990) used the 'Cartes synoptiques' and found evidence for the meridional circulation and the existence of convective giant cells by following the filaments used as indicators of magnetic tracers, and it is very important to understand how the solar dynamo works and therefore the existence of magnetic solar cycles. The phenomenon termed 'rush to the pole' has been confirmed through studying the migration of polar filaments towards the pole at the beginning of solar cycles by many authors (Topka et al 1982;Makarov & Sivaraman 1989;Mouradian & Soru-Escaut 1994;Shimojo et al 2006;Li et al 2008). Solar filaments are distributed over the whole solar surface, from the solar equator to the poles, and during the whole period of a sunspot cycle (Li et al 2007).…”

“…The term 'normal solar activity' is usually applied to solar active events with latitudes lower than 50 • (Sakurai 1998;Li et al 2008), thus here we use filaments with latitudes lower than 50 • . Fig.…”

“…This is clearly visible for latitudes 30 • -90 • . The latitudinal migration of filament activity over the full solar disc was qualitatively introduced by Li et al (2008). In the present study, the catalogue of solar filaments from Carrington solar rotation numbers 876-1823, corresponding to complete cycles 16-21, is used to investigate the latitudinal migration of filaments at low latitudes (less than 50 • ), and the latitudinal drift of solar filaments in each hemisphere in each cycle of the time interval is compared with that of sunspot groups in the same time interval.…”