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.


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Featured Images

Superflare on one of the stars of DG Canum Venaticorum
Tiny Star, Big Outburst Wednesday, December 3, 2014
Three solar flares in early June 2014
Solar Fireworks Thursday, June 12, 2014
One of the first images from IRIS, a new Sun-watching satellite
First Sunlight Wednesday, July 31, 2013
A powerful solar flare erupts on March 6, 2012
Stormy Skies Thursday, March 8, 2012
A January 23, 2012 solar flare
Restless Sun Monday, January 30, 2012
The glow of the aurora from the International Space Station
Heavenly Lightshow Sunday, November 6, 2011
A solar eruption on June 7, 2011
Big Splash Tuesday, June 7, 2011
The Sun as seen from space
Close to the Sun Monday, January 3, 2011
Eruption of gas from the surface of the Sun
Sun Power Wednesday, December 22, 2010
Loopy Sun Friday, April 23, 2010
A Big Bang Tuesday, September 1, 2009
Solar Flare Thursday, July 24, 2008
Reversed Polarity Friday, June 13, 2008
Big Blast Tuesday, May 20, 2008
Active Sun Wednesday, March 26, 2008
Sunny Skies Friday, June 22, 2007
When Sunspots Collide Tuesday, March 27, 2007
All Eyes on the Sun Monday, March 5, 2007
Sunny Skies Tuesday, September 12, 2006
Magnetic Buffer Tuesday, February 7, 2006

Radio Programs

Blackout! The Sun turns out the lights Wednesday, March 12, 2014
Under Attack Earth is attacked by a star Tuesday, October 29, 2013
Storm Probes Plunging into the danger zone Thursday, December 20, 2012
The Sun III Looking for the surface of the Sun Wednesday, December 19, 2012
Looking Deep Looking for storms before they’re born Monday, February 13, 2012
X Factor The Sun’s “X” factor Monday, October 10, 2011
Weather Forecasts Expanding the daily weather forecast Saturday, August 6, 2011
Space Weather Nasty weather from beyond Earth Friday, August 5, 2011
Dangerous Space One of the hazards of space travel Thursday, December 16, 2010
Quiet Sun II A calm and peaceful Sun Sunday, August 22, 2010
Quiet Sun The Sun stays unusually calm Saturday, August 21, 2010
Superstorm! Part 5 The hazards of space weather Friday, September 4, 2009
Superstorm! Part 4 A massive attack from space Thursday, September 3, 2009
Superstorm! Part 3 The Sun delivers a message Wednesday, September 2, 2009
Superstorm! Part 2 The Sun goes haywire Tuesday, September 1, 2009
Superstorm! The Sun sets the night sky on fire Monday, August 31, 2009
Solar Connection Forming a connection with the Sun Tuesday, July 7, 2009
Loud Jupiter A planet that's bright -- and loud Thursday, July 2, 2009
Earth at Aphelion A long snooze for the Sun Wednesday, July 1, 2009
Alpha Centauri B A familiar-looking neighbor Wednesday, April 15, 2009
Northern Darkness The Sun turns out the lights Friday, March 13, 2009


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