Name | Alexander Mordvinov
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Affiliation | ISTP SB RAS, Russia
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Title | Multiple reversals of the Sun's polar-fields and their physical causes
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Authors | A.V Mordvinov, B.B. Karak, D. Banerjee, S. Chatterjee, E.M.Golubeva, A.I. Khlystova
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Abstract | Long-term uniform observations for the past 100 years as recorded at the Kodaikanal Solar Observatory
(KoSO) provide a wealth of information on solar activity. We develop a method for the reconstruction
of the solar magnetic flux using the synoptic observations of the Sun’s emission in the Ca II K and Hα
lines from KoSO. The reconstruction is based on the facts that the Ca II K intensity correlates well with
the unsigned flux, while the sign of the flux is derived from the corresponding Hα map which provides
the information of the dominant polarities. Time-latitude analysis of the reconstructed magnetic flux
depicts an overall view of magnetic field evolution: emergent magnetic flux, its further transformations
with the formation of unipolar magnetic regions and remnant flux surges in Cycles 15-19. We identify
the critical surges of following polarities which result in the regular reversals of the Sun's polar-fields.
The poleward transport of predominantly following polarities contributed much of the polar flux and
led to polar field reversals. Multiple reversals of the Sun’s polar-fields were identified in Cycles 16 and
19. The decay of non-Joy and anti-Hale active regions results in remnant flux surges that disturb the
usual order in magnetic flux transport and sometimes lead to multiple changes of the dominant magnetic
polarities at the Sun’s poles. We found also the remnant flux transport between adjacent 11-year cycles.
These surges indicate a physical connection of subsequent solar cycles. We further analyze evolution
of the Sun’s polar-fields in cycles 21-24. The time-latitudinal analysis of high-resolution synoptic maps
makes it possible to identify surges of leading and following polarities in relation to their sources. All
these analyses improve our understanding of cyclic patterns that demonstrate global reorganization of
the magnetic flux and the polar field buildup. |