A CME, one type of "solar storm", erupts from the Sun in January 2002. The actual disc of the Sun, indicated by the white circle, is hidden in this view through an instrument called a coronagraph. The coronagraph creates an artificial eclipse by blocking the too-bright light from the Sun's surface, allowing us to view the Sun's dimmer atmosphere.
Click on image for full size
Images courtesy SOHO (NASA & ESA). Animation by Windows to the Universe staff (Randy Russell).
Solar Storms
You know, of course, that certain conditions in the Earth's atmosphere can cause powerful storms
like thunderstorms, blizzards, tornadoes, and hurricanes. The Sun also
has an atmosphere, and incredible storms that dwarf Earthly storms sometimes blast forth from the Sun's surface into the solar atmosphere.
The two main types of storms on the Sun are solar
flares and Coronal Mass
Ejections (CMEs). Both storms have to do with tangled magnetic
fields in the neighborhood
of active
regions on the Sun's surface.
Like a rubber band that is twisted until it snaps, the tangled magnetic fields
around an active region release energy when they
"snap". The energy given off in a matter of minutes by a solar flare can be as
much as is given off by 100 hurricanes on Earth!
Solar flares emit energy in
the form of electromagnetic
radiation,
including X-rays, ultraviolet
radiation, visible
light, and radio
waves. A solar flare typically
lasts a few minutes
to as long as an hour.
CMEs are explosions in the corona,
the top part of the Sun's
atmosphere. These explosions
throw out a huge bubble of billions of tons of gas and plasma into
space. A CME typically releases about the same amount of energy as a flare,
but it lasts several hours instead of minutes. If the CME is "aimed" at
Earth, it takes about one to four
days to reach us from the Sun.
The energy from solar storms can be dangerous if it reaches Earth! Astronauts on spacewalks are in danger of increased
radiation exposure, and electronics on satellites can be fried. Earth's
magnetic field and atmosphere shield those of us on the ground from most of
the dangerous radiation thrown out by solar storms.
Sometimes, if we're lucky,
solar storms can offer us a wonderful (safe!) treat. The beautiful displays
of the aurora (Northern and Southern Lights) are results of solar storms.
Some "seasons" are stormier than others on the Sun. Sunspots are more common during "storm seasons"
on the Sun. The number of sunspots rises and falls in an 11-year
cycle, and
an increase in the sunspot count means an increase in solar
activity or solar storms will follow.
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