THE SOLAR CYCLE AT THE MAUNDER MINIMUM EPOCH

Abstract

Here, we present a brief review of the current status of the Maunder minimum study. The Maunder minimum is considered as an example of occasionally occurring Grand minima, when the solar dynamo was in a special mode. We review available sets of direct and indirect data covering the period during and around the Maunder minimum. The start of the minimum was very abrupt and was followed by a gradual recovery of the activity. The data suggest that while the sunspot activity was greatly suppressed during the deep phase of the minimum, the cyclic dynamo kept working around the sunspot formation threshold level, leading to seemingly sporadic occurrence of sunspots. The majority of proxy data depict the dominant 22-year periodicity during the Maunder minimum with the sub-dominant 11-year cycle. The length of the cycles was probably slightly enhanced. We also discuss theoretical models and speculations concerning the solar dynamo as well as the heliosphere during the Maunder minimum. Comparison with other minima (Sporer and Dalton) suggests that these features are common.