Wednesday, January 22, 2014

Why is the sun going quiet?


The sun is our nearest star and the source of all our light and heat on Earth but recent reports have highlighted an ongoing steep decline in solar activity.

This story is a reminder that our sun is a variable star whose dynamic production of magnetism, activity and winds have implications for our planet.

Solar magnetic fields power solar activity, including sunspots, explosive events known as solar flares and coronal mass ejections, and an outward-flowing solar wind.

The sun’s activity and wind bathes Earth in a changing space environment of high-energy radiation and fast-moving particles called “space weather”. This gives us both the beauty of the aurorae and disruptive effects on communications and other technology.

Solar activity varies over time, with the 11-year sunspot cycle being the most familiar example. Solar activity also varies more widely over longer timescales, producing “grand maxima” and “grand minima”.
The most famous of these is the Maunder minimum in sunspot activity from around 1645 to 1715.

The current rate and extent at which solar activity is falling has been interpreted as the beginning of another grand minimum, and raises the issue of what it means for Earth’s climate.
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