1650-1715: The Maunder minimum
Sunspots observations continued in the seventeenth century,
with the most active observers being the German
Johannes Hevelius (1611-1687)
and the Jesuit Jean Picard (1620-1682). Very few sunspots
were observed from about 1650 to 1715, and when they were
their presence was noted as a noteworthy event
by active astronomers. Historical reconstructions of sunspot
numbers indicate that the dearth of sunspots is real, rather
than the consequence of a lack of diligent observers.
A simulatenous decrease in auroral counts further suggest that
solar activity was greatly reduced during this time period.
Variation in observed sunspot numbers during the time period
1600-1800. The yellow curve is the Wolf sunspot number, and the
purple line a count of sunspot groups based on a reconstruction
by D.V. Hoyt. The green crosses are auroral counts, based on
a reconstruction by K. Krivsky and J.P. Legrand.
This period is now known as the Maunder minimum, after the solar
astronomer E.W. Maunder, who was most active in investigating the
dearth of sunspot sightings by astronomers active in the second
half of the seventeenth century. The documented
occurrence of exceptionally cold winters throughout Europe
during those years may be causally related to reduced solar
activity
On the Maunder minimum:
Eddy, J.A. 1976 Science, 192, 1189-1203.
Riber, J.C., & Nesme-Ribes, E. 1993, Astronomy & Astrophysics,
276, 549-563.
Hoyt, D.V. & Schatten, K.H. 1997, The Role of the Sun in
Climate Change, Oxford University Press.
