Mathematics – Logic
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd...8e..18k&link_type=abstract
Solar and Stellar Activity Cycles, 26th meeting of the IAU, Joint Discussion 8, 17-18 August 2006, Prague, Czech Republic, JD08,
Mathematics
Logic
Scientific paper
This investigation is devoted to theoretical explanation of the observed north-south Sun's magnetic asymmetry. We studied the conditions of magnetic field generation by αΩ-dynamo in the region close to the tachocline for the solar convection zone (SCZ) model by Stix (1989, The Sun, Berlin), using the helioseismological data on the solar internal rotation rate Ω during the rising phase of the 23^rd cycle (Howe et al. 2000, Sci 287, 2456). The recent helioseismology inversions had revealed that the rotation rate in the SCZ can be divided into domains with opposite signs of the radial angular-velocity gradient ∂Ω/∂r. One domain is situated at mid to low latitudes where ∂Ω/∂r > 0 and another two domains (one by one in each hemisphere) - at high latitudes where ∂Ω/∂r < 0. Discovery by helioseismology two different regimes of the internal rotation in the SCZ is most important for explanation of the observed magnetic anomalies since the threshold for exciting the global magnetic field modes (dipole or quadrupole) depends on the sign of the product αΩ (α is the helicity parameter). Also we have taken into account the negative α-effect near the bottom of the SCZ (Krivodubskij 2005, AN 326, 61). It was found that the conditions near the tachocline leads to two magnetic mixed-parity solutions. Namely at the near-equator region the αΩ-dynamo mechanism can reproduce the mixed-parity of the first type in which the dipole mode is predominant over the quadrupole component. While at the high latitudes the quadrupole mode can be excited more effectively than dipole one (the mixed-parity solution of the second type). This leads to specific north-south magnetic asymmetry during solar cycle. At the epoch of reversal of polar fields, when energy of dipole is exhausted in most degree, the favorable conditions spring up for observing of quadrupole mode (the apparent magnetic "monopole" near the maxima of solar cycles). Furthermore, the first mixed-parity solution is relevant to the properly-oriented magnetic regions (Hale's law) while the second type of solution very likely could account for the reversed polarity regions (located within near equator zone) for the maximum epoch and during the declining of solar cycles.
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