40 research outputs found
The asymmetry of sunspot cycles and Waldmeier relations as due to nonlinear surface-shear shaped dynamo
The paper presents a study of a solar dynamo model operating in the bulk of
the convection zone with the toroidal magnetic field flux concentrated in the
subsurface rotational shear layer. We explore how this type of dynamo may
depend on spatial variations of turbulent parameters and on the differential
rotation near the surface. The mean-field dynamo model takes into account the
evolution of magnetic helicity and describes its nonlinear feedback on the
generation of large-scale magnetic field by the -effect. We compare the
magnetic cycle characteristics predicted by the model, including the cycle
asymmetry (associated with the growth and decay times) and the duration -
amplitude relation (Waldmeier's effects), with the observed sunspot cycle
properties. We show that the model qualitatively reproduces the basic
properties of the solar cycles.Comment: 28 pages, 7 figures(Second revision, figures updates
Photospheric Magnetic Field: Relationship Between North-South Asymmetry and Flux Imbalance
Photospheric magnetic fields were studied using the Kitt Peak synoptic maps
for 1976-2003. Only strong magnetic fields (B>100 G) of the equatorial region
were taken into account. The north-south asymmetry of the magnetic fluxes was
considered as well as the imbalance between positive and negative fluxes. The
north-south asymmetry displays a regular alternation of the dominant hemisphere
during the solar cycle: the northern hemisphere dominated in the ascending
phase, the southern one in the descending phase during Solar Cycles 21-23. The
sign of the imbalance did not change during the 11 years from one polar-field
reversal to the next and always coincided with the sign of the Sun's polar
magnetic field in the northern hemisphere. The dominant sign of leading
sunspots in one of the hemispheres determines the sign of the magnetic-flux
imbalance. The sign of the north-south asymmetry of the magnetic fluxes and the
sign of the imbalance of the positive and the negative fluxes are related to
the quarter of the 22-year magnetic cycle where the magnetic configuration of
the Sun remains constant (from the minimum where the sunspot sign changes
according to Hale's law to the magnetic-field reversal and from the reversal to
the minimum). The sign of the north-south asymmetry for the time interval
considered was determined by the phase of the 11-year cycle (before or after
the reversal); the sign of the imbalance of the positive and the negative
fluxes depends on both the phase of the 11-year cycle and on the parity of the
solar cycle. The results obtained demonstrate the connection of the magnetic
fields in active regions with the Sun's polar magnetic field in the northern
hemisphere.Comment: 24 pages, 12 figures, 2 table