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Solar Cycle 25 has started! Earlier this month, the official Solar Cycle 25
Prediction Panel, announced that solar minimum occurred in December
2019. The sun has an cycle of
around 11 years, starting with a minimum in solar activity, and
reaching a maximum about half-way through the cycle. As the Sun
is quite variable, it takes some time to determine when the minimum has
been reached. The solar cycle is tracked by monitoring sunspots --
the dark blotches on the Sun that are associated with solar activity.
Solar cycle 1 was the first solar cycle since detailed recording of
solar sunspot activity began, with solar cycle 1 beginning in February
1755. The solar cycle dictates what we can expect in terms of space
weather: outbursts from the Sun can result in a range of effects, from
aurorae to satellite orbital decay, and disruptions to radio
communications or the power grid. The visible light images above are
from NASA's Solar Dynamics Observatory and show the Sun at solar
minimum in December 2019 and the last solar maximum in April
2014. Sunspots are visible on the Sun during solar maximum. (Image
credits: NASA's Solar Dynamics Observatory/Joy Ng)
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