5 Amplitude Fluctuations, Multiperiodicity, and Grand Minima

Since the basic physical mechanism(s) underlying the operation of the solar cycle are not yet agreed upon, attempting to understand the origin of the observed fluctuations of the solar cycle may appear to be a futile undertaking. Nonetheless, work along these lines continues at full steam in part because of the high stakes involved; varying levels of solar activity may contribute significantly to climate change (see Haigh, 2007, and references therein). Moreover, the frequencies of all eruptive phenomena relevant to space weather are strongly modulated by the amplitude of the solar cycle. Finally, certain aspects of the observed fluctuations may actually hold important clues as to the physical nature of the dynamo process.

 5.1 The observational evidence: An overview
 5.2 Fossil fields and the 22-yr cycle
 5.3 Dynamical nonlinearity
  5.3.1 Backreaction on large-scale flows
  5.3.2 Dynamical α-quenching
 5.4 Time-delay dynamics
  5.4.1 Time-delays in Babcock–Leighton models
  5.4.2 Reduction to an iterative map
 5.5 Stochastic forcing
 5.6 Intermittency
  5.6.1 The Maunder Minimum and intermittency
  5.6.2 Intermittency from stochastic noise
  5.6.3 Intermittency from nonlinearities
  5.6.4 Intermittency from threshold effects
  5.6.5 Intermittency from time delays
 5.7 Solar cycle predictions based on dynamo models

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