Active longitudes and north-south asymmetry of the activity the Sun as manifestations of its relic magnetic field

Мордвинов, А. В.; Kitchatinov, L. L.

doi:10.1134/1.1687019

Cited by 16 publications

(11 citation statements)

References 16 publications

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“…From flare positions 26.72 and 26.61 days (Bai, 1988), 27.41 days in Cycles 19 -21 (Bai, 2003), and 22.169 days (Jetsu et al, 1997) have been found. The radiation zone rotation period of 28.8 days has been found on synoptic maps of photospheric magnetic fields with special filtering techniques by Mordvinov and Kitchatinov (2004). However, the different rotation periods do not necessarily suggest mistakes or methodological artifacts; some of the differences may be explained by a varying migration pattern as demonstrated by Juckett (2006).…”

Section: Introductionmentioning

confidence: 91%

Migration and Extension of Solar Active Longitudinal Zones

2013

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Solar active longitudes show a characteristic migration pattern in the Carrington coordinate system when they can be identified at all. By following this migration, the longitudinal activity distribution around the center of the band can be determined. The halfwidth of the distribution is found to be varying in Cycles 21 - 23, and in some time intervals it was as narrow as 20 - 30 degrees. It was more extended around maximum but it was also narrow when the activity jumped to the opposite longitude. Flux emergence exhibited a quasi-periodic variation within the active zone with a period of about 1.3 years. The path of the active longitude migration does not support the view that it might be associated with the 11-year solar cycle. These results were obtained for a limited time interval of a few solar cycles and, bearing in mind uncertainties of the migration path definition, are only indicative. For the major fraction of dataset no systematic active longitudes were found. Sporadic migration of active longitudes was identified only for Cycles 21 - 22 in the northern hemisphere and Cycle 23 in the southern hemisphere.Comment: 16 pages, 6 figure

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Section: Introductionmentioning

confidence: 91%

Migration and Extension of Solar Active Longitudinal Zones

2013

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“…The concept of a relic magnetic field hidden within the solar radiative zone, as well as its possible manifestation in the form of an nonaxisymmetric magnetic field configuration has been discussed a number of times (e.g. Dicke 1979;Kitchatinov et al 2001;Mordvinov & Kitchatinov 2004). For example, Kitchatinov et al (2001) suggest that a relic field is captured, producing a nonaxisymmetric structure with strength somewhat below 1 G. Taking into account the discrepancy between the amplitudes of toroidal and poloidal magnetic field at the solar surface and the stretching of the toroidal field in the tachocline region, manifestation of an active longitude phenomenon in a form comparable with observations is possible.…”

Section: Beyond a Dynamo Explanationmentioning

confidence: 99%

Active longitudes, nonaxisymmetric dynamos and phase mixing

Berdyugina

Moss

Sokoloff

et al. 2005

A&A

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We discuss the problem of solar active longitudes from the viewpoint of dynamo theory. We start from a recent observational analysis of the problem undertaken by Berdyugina & Usoskin (2003, A&A, 405, 1121 and Usoskin et al. (2005, A&A, 441, 347) who demonstrated from a study of sunspot data that solar active longitudes rotate differentially, with a small but significant asynchrony between northern and southern hemispheres. We suggest two concepts by which the underlying magnetic structure could lead to the observed phenomenologythe true differential rotation of a nonaxisymmetric magnetic structure and a stroboscopic effect. In the latter case, a solid body rotation of nonaxisymmetric magnetic structure is illuminated by an activity wave propagating from middle latitudes to the solar equator, and so mimics a differential rotation. We then discuss several mechanisms which could in principle lead to the excitation of active longitudes. In particular, we consider dynamo excitation of nonaxisymmetric magnetic modes, nonaxisymmetric structures as a manifestation of a relic magnetic field in the solar core, nonaxisymmetric solar hydrodynamics and nonlinear instabilities that lack axial symmetry. We conclude that these mechanisms all provide ways to explain the phenomenology, provided the stroboscopic interpretation is accepted. Of course, a quantitative explanation in the framework of any scenario requires ultimately a detailed numerical simulation. The interpretation of the available observations as a true differential rotation appears to provide a much more severe challenge for theorists. We are unable to suggest a plausible mechanism of this kind; however we can not exclude in principle such an explanation. We relate the phenomenon of solar active longitudes to the information available concerning stellar active longitudes, and also consider evidence from other tracers of solar activity.

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“…Although the existence of preferred longitudes of sunspot formation (active longitudes) has been suggested long ago, the question of their persistency was still a subject of ongoing debates (e.g., Chidambara 1932; Lopez Arroyo 1961; Balthasar & Schüssler 1983;Vitinsky et al 1986;Mordvinov & Kitchatinov 2004). A novel analysis of sunspot group data for the past 120 years revealed the existence of two persistent active longitudes separated by 180…”

Section: Introductionmentioning

confidence: 99%

Preferred sunspot longitudes: non-axisymmetry and differential rotation

Usoskin¹,

Berdyugina²,

Poutanen³

2005

A&A

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Abstract.As recently found, the distribution of sunspots is non-axisymmetric and spot group formation implies the existence of two persistent active longitudes separated by 180• . Here we quantitatively study the non-axisymmetry of sunspot occurrence. In a dynamic reference frame inferred from the differential rotation law, the raw sunspot data show a clear clustering around the persistent active longitudes. The differential rotation describing the dynamic frame is quantified in terms of the equatorial angular velocity and the differential rotation rate, which appear to be significantly different from those for individual sunspots. This implies that the active longitudes are not linked to the depth of sunspot anchoring. In order to quantify the observed effect, we introduce a measure of the non-axisymmetry of the sunspot distribution. The non-axisymmetric component is found to be highly significant, and the ratio of its strength to that of the axisymmetric one is roughly 1:10. This provides additional constraints for solar dynamo models.

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Active longitudes and north-south asymmetry of the activity the Sun as manifestations of its relic magnetic field

Cited by 16 publications

References 16 publications

Migration and Extension of Solar Active Longitudinal Zones

Migration and Extension of Solar Active Longitudinal Zones

Active longitudes, nonaxisymmetric dynamos and phase mixing

Preferred sunspot longitudes: non-axisymmetry and differential rotation

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