Solar flares are short-term
outbursts on the sun, caused by the sudden release of energy
stored in twisted magnetic fields in the solar atmosphere. Flares
are more contained than
coronal mass ejections
still release up to 10
joules of energy—the
energy equivalent of ten million volcanic eruptions. They can last
just a few minutes or up to several hours.
Flares occur in active regions, areas on the sun
where the magnetic fields are very strong. In this ultraviolet
light image of the sun on the right, the active regions stand out
as bright spots or clusters of spots. (In visible light images
of the sun, the dark spots you see—called sunspots—are
active regions.) By the way, the green color isn’t real:
color chosen to represent ultraviolet light, which is invisible
to our eyes.
Look at the current image of the sun on the lower
right. Do you see any bright spots or clusters? These are active
regions, sites for possible solar flares.
Solar flares fling tremendous amounts of energy
into space, including high-energy particles (protons, electrons,
and atomic nuclei) and electromagnetic radiation ranging from gamma
rays and X-rays to radio waves. Radiation travels at the breakneck
speed of light—186,000 miles/second (300,000 kilometers/second)—so
X-rays, gamma rays, and radio waves are the first evidence of a
flare to reach the earth, which happens in about 8 minutes. Particles
travel more slowly, taking anywhere from about 30 minutes (for
higher energy particles) to several days to reach the earth. When
electromagnetic radiation and particles from flares do reach the
earth, they can cause
, including disruptions in communications.
Look for current solar flares using
An active region of the sort that
can give rise to solar flares.