Open AccessEvidence for a long‐term variation of the dynamo action responsible for the solar magnetic cycle
Author(s) -
Lopes I.,
Passos D.
Publication year - 2009
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2009.14910.x
Subject(s) - physics , dynamo , solar dynamo , sunspot , dynamo theory , solar cycle , magnetic field , interplanetary magnetic field , secular variation , dipole model of the earth's magnetic field , variation (astronomy) , astrophysics , mercury's magnetic field , astronomy , solar wind , quantum mechanics
By using the sunspot time series as a proxy, we have made a detailed analysis of the mean solar magnetic field over the last two and half centuries, by means of a reconstruction of its phase space. We find evidence of a long‐term trend variation of some of the solar physical processes (over a few decades) that might be responsible for the apparent erratic behaviour of the solar magnetic cycle. The analysis is done by means of a careful study of the axisymmetric dynamo model equations, where we show that the temporal counterpart of the magnetic field can be described by a self‐regulated two‐dimensional dynamic system, usually known as a Van der Pol–Duffing oscillator. Our results suggest that during the last two and half centuries, the velocity of the meridional flow, v p , and the efficiency of the α mechanism responsible for the conversion of toroidal magnetic field into poloidal magnetic field might have suffered variations that can explain the observed variability in the solar cycle.