= Solar grand minimum
= Solar grand minima
{synonym}
A solar grand minimum is a prolonged interval, lasting several ordinary cycles, of strongly reduced sunspot activity. Historical records identify the <Maunder minimum>; cosmogenic carbon-14 and beryllium-10 provide longer indirect records because stronger heliospheric magnetic shielding generally reduces cosmic-ray production of these isotopes. Weak activity does not imply a zero <solar magnetic field>. Proposed causes include stochastic weakening of poloidal-field generation, nonlinear dynamo modulation, and intermittency near an excitation threshold.
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