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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.


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

Our Star, the Sun June 8, 2006

Featured Images

an x-flare erupts from the sun

X Flare! November 29, 2023

An explosion from the surface of the Sun

Blowing Bubbles June 12, 2023

new images of sunspots

Stormy Sun May 27, 2023

the Sun in December 2019, at solar minimum

Livelier Sun May 1, 2023

mine explosion in vietnam

Solar Booms August 4, 2022

Sun from Solar Dynamics Observatory

Changing Sun May 31, 2022

eruption on the Sun

Unexpected Storm April 12, 2022

New York Railroad Storm, 1921

Nasty Storm May 12, 2021

A solar flare erupting on April 22, 2021

A Big Blast April 22, 2021

Ultraviolet images of the Sun from Solar Orbiter

Here Comes the Sun July 17, 2020

Coronal mass ejection from the Sun

Nasty Outburst June 17, 2019

Solar storm, May 2019

Storm to Storm May 15, 2019


Dark Storms May 18, 2018

Powerful solar flare, September 6, 2017

Solar Storm September 6, 2017

A 2015 solar flare

Scary Storm May 28, 2017

Major Storm March 23, 2017

ALMA view of a sunspot

Giant Storm January 19, 2017

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

Radio Programs

X Flares The Sun’s “X” factor November 29, 2023

Pesky Auroras The Sun makes a nuisance of itself September 9, 2023

Magnetic Blemishes Blemishes on the face of a star June 12, 2023

Unruly Sun The Sun gets a little unruly May 1, 2023

Solar Rain Watching it rain — on the Sun March 16, 2023

Stormy Skies Stormy Sun, stormy Earth February 16, 2023

Gustav Spörer Learning about solar “naps” October 23, 2022

Matching Storms The Sun helps El Niño August 8, 2022

Solar Trigger Big explosions trigger smaller ones August 4, 2022

New York Railroad Storm Stormy days for railroads and telegraphs May 12, 2021

Solar Sneezes Nasty “sneezes” from the Sun May 11, 2021

Spoerer Minimum A time when the Sun was quiet March 23, 2021

Seeing Sunspots Counting future spots on the Sun March 22, 2021

Stellar Magnets Turning stars into magnets February 9, 2021

Superflares Super outbursts from the Sun February 5, 2020

Solar Orbiter Flying into the solar wind February 4, 2020

Solar Telescope Watching the Sun from the house of the Sun January 23, 2020

Lacerta A little star with a big punch September 15, 2019

Changing Sun A big change for the Sun September 14, 2019

Big Storm A big storm on the Sun June 17, 2019

Solar Minimum The Sun takes it easy April 2, 2019

Cosmic Hazards If it’s not one thing, it’s another May 31, 2018

Dark Storms Dark storms on the surface of the Sun May 18, 2018

More Eclipse Science Chasing a shadow from the sky August 17, 2017

Storm Damage Risks from storms on the Sun June 23, 2017

Quiet Sun A long period of rest for the Sun June 22, 2017

Busy Sun Some busy years for the Sun June 21, 2017

Star War Solar storms and a military alert May 29, 2017

Quiet Sun Cosmic bombardment in tree rings April 5, 2017

Storm Impact Projecting damages from a big storm March 23, 2017

Counting Starspots Counting spots on a small star March 3, 2017