Evolution and rotation of large-scale photospheric magnetic fields of the Sun during cycles 21–23

Abstract

Abstract. We present the results of an extensive time series analysis of longitudinally-averaged synoptic maps, recorded at the National Solar Observatory (NSO/Kitt Peak) from 1975 to 2003, and provide evidence for a multitude of quasi-periodic oscillations in the photospheric magnetic field of the Sun. In the low frequency range, we have located the sources of the 3.6 yr, 1.8 yr, and 1.5 yr periodicities that were previously detected in the north-south asymmetry of the unsigned photospheric flux (Knaack et al. 2004, A&A, 418, L17). In addition, quasi-periodicities around 2.6 yr and 1.3 yr have been found. The 1.3 yr period is most likely related to large-scale magnetic surges toward the poles and appeared in both hemispheres at intermediate latitudes ∼30• -55• during the maxima of all three cycles 21-23, being particularly pronounced during cycle 22. Periods near

Stability of latitudinal differential rotation in stars

“…If this is the case, transequatorial vortices (unstable S1 modes) should be present near the base. The rates of (retrograde) drift of the vortices are similar to that of the r-modes signatures inferred by Knaack et al (2005) from solar magnetograms.…”

“…Excitation of r-modes of global oscillations in differentially rotating neutron stars is considered as a source of detectable gravitational waves (Watts et al 2003). Knaack et al (2005) interpreted the large-scale structures in magnetic fields of the Sun as signatures of r-modes, which may in turn result from an instability.…”

Periodicities in the X-Ray Emission From the Solar Corona

“…181 days 176; 175; 182; 187 days Occurrence of solar type III radio burst during minimum phase of cycle 23 (Lobzin et al 2012); solar electron flare occurrence during cycle 23 (Chowdhury & Ray 2006); solar wind velocity and DST index (Katsavrias et al 2012); sunspot area of whole sphere for cycle 23 (Chowdhury et al 2009) 8. 227 days 209-222; 226 days Variation of the photospheric magnetic flux (Knaack et al 2005); X-ray flares of B & C classes for cycle 23 (Dimitropoulou et al 2008) 9. 303 days 310; 313 days Occurrence rate of solar proton flares; IMF (B y component) (Katsavrias et al 2012) 10.…”

“…They found significant power with a 1.28 yr period, however, it was observed to vary strongly with time. A 1.3 yr periodicity has also been detected in variations of the interplanetary magnetic field and geomagnetic activity (Paularena et al 1995;Szabo et al 1995;Lockwood 2001;Mursula et al 2003;Katsavrias et al 2012) as well as in the variation of the photospheric magnetic flux (Knaack et al 2005) and in the solar wind speed (Richardson et al 1994;Prabhakaran Nayar et al 2002). Based on an analysis of the same data, however, Antia & Basu (2000) drew conclusions that contradict those of Howe et al (2000).…”

“…The range of timescales between these extremes (27 days and 11 yr) is called "mid-range" or "intermediate-term" periodicity. Studies of short-and mid-term variations in solar activity and their solar-cycle dependence may help us to achieve a better understanding of the basic processes of the solar activity cycle; the dynamics and mechanisms of the generation of the solar magnetic field; and predicting the level of solar activity (Sturrock & Bai 1992;Krivova & Solanki 2002;Knaack et al 2005;Atac &Özgüc 2006;Obridko & Shelting 2007), and hence the variation in space weather (Bhatt et al 2009). …”