THE MAUNDER MINIMUM
The Maunder Minimum (also known as the prolonged sunspot minimum) is the name used for the period starting in about 1645 and continuing to about 1715 when sunspots became exceedingly rare, as noted by solar observers of the time.
It caused London’s River Thames to freeze over, and ‘frost fairs’ became popular.
The Frozen Thames, 1677 – an oil painting by Abraham Hondius shows the old London Bridge during the Maunder Minimum
This period of solar inactivity also corresponds to a climatic period called the “Little Ice Age” when rivers that are normally ice-free froze and snow fields remained year-round at lower altitudes.
There is evidence that the Sun has had similar periods of inactivity in the more distant past, Nasa says.
The connection between solar activity and terrestrial climate is an area of on-going research.
‘Sunspot numbers are well below their values from 2011, and strong solar flares have been infrequent,’ the space agency says.
The image above shows the Earth-facing surface of the Sun on February 28, 2013, as observed by the Helioseismic and Magnetic Imager (HMI) on NASA’s Solar Dynamics Observatory.