N–S Asymmetry in the Solar Differential Rotation During 1957–1993

Gigolashvili, M. Sh.; Japaridze, D. R.; Mdzinarishvili, T. G.; Chargeishvili, B. B.

doi:10.1007/s11207-005-1214-3

Cited by 40 publications

(18 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For example, it has been found that the northern hemisphere rotates faster during even cycles (20 and 22), while the rotation of the southern hemisphere dominates in odd ones (cycles 19 and 21; Gigolashvili et al 2005), a property that has been also interpreted with theoretical arguments ( Itoh et al 2005).…”

Section: North-south Asymmetrymentioning

confidence: 90%

Coronal Rotation at Solar Minimum from UV Observations

Giordano

Mancuso

2008

Astrophysical Journal

View full text Add to dashboard Cite

The observations of the UVCS SOHO instrument from 1996 May to 1997 May have been analyzed to reconstruct intensity time series of the O vi 1032 8 and H i Ly 1216 8 spectral lines at different coronal heliolatitudes from 1.5 to 3.0 R from Sun center. At solar minimum, some features persist for several rotations, thus allowing analysis of the UV emission as time series modulated at the period of the solar rotation. We find evidence of coronal differential rotation, which significantly differs from that of the photospheric plasma. The estimated equatorial synodic rotation period of the corona at 1.5 R is 27:48 AE 0:10 days. The study of the latitudinal variation shows that the UV corona decelerates toward the photospheric rates from the equator up to the poleward boundary of the midlatitude streamers, reaching a peak of 28:16 AE 0:20 days around +30 from the equator at 1.5 R , while a less evident peak is observed in the northern hemisphere. This result suggests a real north-south rotational asymmetry as a consequence of different activity and weak coupling between the magnetic fields of the two hemispheres. The study of the radial rotation profiles shows that the corona is rotating almost rigidly with height, but we find an abrupt increase by about half a day between 2.3 and 2.5 R . The larger gradients of the rotation rates are localized at the boundaries between open and closed field lines, suggesting that in these regions the differential rotation might be a source of magnetic stress and, consequently, of energy release.

show abstract

Section: North-south Asymmetrymentioning

confidence: 90%

Coronal Rotation at Solar Minimum from UV Observations

Giordano

Mancuso

2008

Astrophysical Journal

View full text Add to dashboard Cite

show abstract

“…Hansen & Hansen 1975;Duchlev 2001;Gigolashvili et al 2005), and photospheric magnetic fields (e.g. Antonucci et al 1990;Mouradian & Soru-Escaut 1991;Knaack et al 2004Knaack et al , 2005.…”

Section: Introductionmentioning

confidence: 99%

Hemispheric sunspot numbers ${R_{n}}$ and ${R_{s}}$ from 1945–2004: catalogue and N-S asymmetry analysis for solar cycles 18–23

Temmer

Rybák

Bendík

et al. 2006

A&A

178

148

View full text Add to dashboard Cite

From sunspot drawings provided by the Kanzelhöhe Solar Observatory, Austria, and the Skalnaté Pleso Observatory, Slovak Republic, we extracted a data catalogue of hemispheric Sunspot Numbers covering the time span 1945−2004. The validated catalogue includes daily, monthlymean, and smoothed-monthly relative sunspot numbers for the northern and southern hemispheres separately and is available for scientific use. These data we then investigated with respect to north-south asymmetries for almost 6 entire solar cycles (Nos. 18−23). For all the cycles studied, we found that the asymmetry based on the absolute asymmetry index is enhanced near the cycle maximum, which contradicts to previous results that are based on the normalized asymmetry index. Moreover, the weak magnetic interdependence between the two solar hemispheres is confirmed by their self-contained evolution during a cycle. For the time span 1945−2004, we found that the cycle maxima and also the declining and increasing phases are clearly shifted, whereas the minima seem to be in phase for both hemispheres. The asymmetric behavior reveals no obvious connection to either the sunspot cycle period of ∼11-or the magnetic cycle of ∼22-years. The most striking excess of activity is observed for the northern hemisphere in cycles 19 and 20.

show abstract

“…It is possible to see that Hα filaments and the long-lived magnetic features reveal asymmetry in rotation rate for investigated period (1966)(1967)(1968)(1969)(1970)(1971)(1972)(1973)(1974)(1975)(1976)(1977)(1978)(1979)(1980)(1981)(1982)(1983)(1984)(1985). The N-S asymmetry of rotation rates needs further studies and it will be the subject of our future investigations, carried out by improved statistical investigation, than we used for Hα filaments in earlier works (Gigolashvili et al, 2005;.…”

Section: Discussionmentioning

confidence: 99%

“…Besides sunspots, other features of the solar atmosphere used as tracers of solar rotation are e.g., faculae (Newbegin, and Newton, 1931) and Hα filaments (D'Azambuja and D'Azambuja, 1948;Japaridze and Gigolashvili, 1992;Gigolashvili et al, 1995;Gigolashvili et al, 2003Gigolashvili et al, , 2005Gigolashvili et al, , 2007Gigolashvili, Japaridze, and Kukhianidze, 2005).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Investigation of the Differential Rotation by Hα Filaments and Long-Lived Magnetic Features for Solar Activity Cycles 20 and 21

2012

Self Cite

View full text Add to dashboard Cite

Abstract. For solar activity cycles 20 and 21 (1966-1985) the solar differential rotation has been investigated using Hα filaments and relatively small-scale long-lived magnetic features with negative and positive polarities. We used annual averaged angular velocities of quiescent Hα filaments from Hα photoheliograms of the Abastumani Astrophysical Observatory film collection and selected long-lived magnetic features from the McIntosh atlas (McIntosh, Willock, and Thompson, Atlas of Stackplots, NGDC, 1991). We have determined coefficients of Faye's formulas for Hα filaments as well as for long-lived magnetic features and have found that for solar cycles 20 and 21 the Hα filaments have lower rotation rates and rotated more differentially than the long-lived magnetic features.

show abstract

N–S Asymmetry in the Solar Differential Rotation During 1957–1993

Cited by 40 publications

References 17 publications

Coronal Rotation at Solar Minimum from UV Observations

Coronal Rotation at Solar Minimum from UV Observations

Hemispheric sunspot numbers ${R_{n}}$ and ${R_{s}}$ from 1945–2004: catalogue and N-S asymmetry analysis for solar cycles 18–23

Investigation of the Differential Rotation by Hα Filaments and Long-Lived Magnetic Features for Solar Activity Cycles 20 and 21

Contact Info

Product

Resources

About