Solar Polar Fields and the 22-Year Activity Cycle: Observations and Models
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We explore observations and models of the interacting, cyclical behavior of the active regions and the polar magnetic fields of the Sun. We focus on observational evidence of these fields interacting across the corridor between active and polar latitudes. We present observations of diverse magnetic signatures on, above and beneath the solar surface, and find much evidence of phenomena migrating in both directions across this corridor in each hemisphere, including photospheric fields, ephemeral bipoles, interior torsional oscillations, high-latitude filaments, and coronal green line intensity. Together these observations produce a complex physical picture of high-latitude solar magnetic field evolution in the photosphere, atmosphere and interior, and demonstrate their essential role in the solar cycle. The picture presented by these collected observations is consistent with the Babcock-Leighton phenomenological model for the cycle, and we discuss related efforts to predict cycle amplitudes based on polar field strengths and on combining activity and polar-field information in a single phase-independent, slowly-evolving index. We also briefly review related work on magnetic flux transport models for the solar cycle, with particular reference to the interaction between flux emergence patterns and meridional flows.
KeywordsSolar magnetic fields Activity cycle Solar poles Photosphere Chromosphere Corona Solar interior Magnetic flux-transport models
The authors are grateful to A. Balogh for the opportunity to participate in the ISSI Workshop on “The Solar Activity Cycle: Physical Causes and Consequences”, held in November 2013. KP acknowledges support from the Hungarian Science Research Fund (OTKA grants no. K83133 and 81421). KS appreciates the support of GSFC-NASA’s code 500/590 involving Mission Operations, and a.i.-solutions, inc., as well as valuable discussions with Hans Mayr.
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