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Sunspots and Solar Flares

A sunspot is a cooler, and therefore darker, region of the Sun’s photosphere caused by a solar magnetic disturbance. Strong, dense magnetic fields generated by circulating plasma sometimes become entangled and surge through the photosphere, creating the sunspot. The knot causes the temperature to fall to around 1000 K in the sunspot region, which darkens the photosphere. The dark center of the sunspot is called the umbra, and it is surrounded by a dim filamentary area called the penumbra. Sunspots range from Earth-size “pimples” to swollen scars halfway across the surface. Sunspot activity generally follows an 11-year cycle, called the “sunspot cycle.” A solar flare is a violent eruption of plasma from the chromosphere of the Sun that is whipped up by intense magnetic activity. During the eruption, flares rise thousands of kilometers above the chromosphere, and the plasma temperatures quickly soar to 20 million degrees. Large flares release 10^25 Joules, or about the energy of a few million volcanic eruptions on the Earth. Sunspot and solar flare frequency are strongly related. In addition, flares often disturb the Earth’s atmosphere electrically, thus interfering with radio transmissions. The aurora borealis and aurora australis are results of flare activity that injects energetic particles into Earth’s magnetic field.

Resources

A giant plume of hot gas explodes from the Sun's surface. Giant bubbles of hot g

Our Star, the Sun June 8, 2006

Radio Programs

Nanoflares “Little” explosions from the Sun July 12, 2016

Rudolf Wolf A cycle of storms on the Sun July 7, 2016

Herbert Friedman Watching the Sun with a “rockoon” June 21, 2016

Zapped! Zapped by the Sun — twice January 18, 2016

Solar Nap The Sun takes a long nap April 29, 2015

Unpredictable Sun Predicting our unpredictable Sun April 28, 2015

Solar Max Taking a look at the busy Sun February 13, 2015

Blackout! The Sun turns out the lights March 11, 2014

Under Attack Earth is attacked by a star October 28, 2013

Storm Probes Plunging into the danger zone December 19, 2012

The Sun III Looking for the surface of the Sun December 18, 2012

Looking Deep Looking for storms before they’re born February 12, 2012

X Factor The Sun’s “X” factor October 9, 2011

Weather Forecasts Expanding the daily weather forecast August 5, 2011

Space Weather Nasty weather from beyond Earth August 4, 2011

Featured Images

Space-based view of a powerful solar flare

Big Blast January 18, 2016

Image of a powerful solar flare on March 11, 2015

Solar Flare March 12, 2015

Artist's concept of Solar Max in orbit

Sun Watcher February 14, 2015

Composite image of the Sun

Hot Sun December 24, 2014

Superflare on one of the stars of DG Canum Venaticorum

Tiny Star, Big Outburst December 3, 2014

Three solar flares in early June 2014

Solar Fireworks June 12, 2014

One of the first images from IRIS, a new Sun-watching satellite

First Sunlight July 31, 2013

A powerful solar flare erupts on March 6, 2012

Stormy Skies March 8, 2012

A January 23, 2012 solar flare

Restless Sun January 30, 2012

The glow of the aurora from the International Space Station

Heavenly Lightshow November 6, 2011

A solar eruption on June 7, 2011

Big Splash June 7, 2011

The Sun as seen from space

Close to the Sun January 3, 2011

Eruption of gas from the surface of the Sun

Sun Power December 22, 2010

Loopy Sun April 23, 2010