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Paper: Coherent Structures vs Independent Modes of the Axisymmetric Magnetic Field Fluctuations
Volume: 346, Large-scale Structures and their Role in Solar Activity
Page: 91
Authors: Cadavid, A.; Lawrence, J.; McDonald, D.; Ruzmaikin, A.
Abstract: Quasi periodicities on scales of 1 to 2.5 years have been observed in solar, interplanetary and geomagnetic time series. The relation of these signals to 1 and 1.3 yr fluctuations in the solar interior suggest the presence of structures or characteristic modes in the magnetic field, generated by the dynamo, that extend into the heliosphere. We have applied the methods of principal component analysis (PCA) and independent component analysis (ICA) to search for the coherent structures (PCA) and independent global modes (ICA) of the axisymmetric solar magnetic field. While PCA is effective in identifying the coherent modes that describe the 22 yr solar cycle, ICA uncovers the independent global modes with characteristic 1 to 2.5 yr quasi periods observed in heliospheric and helioseismic time series. Five modes capture the salient properties of the data. Two modes describe the polar and high latitude fields, and present 1-1.5 yr quasi periodicities. The other three modes correspond to low and mid-latitude phenomena and show both 1.3 yr and 1.7 yr variations.
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