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SOLAR
WINDS AND CMES
 Eruptions
on the Sun's surface occur often. During
normal solar activity the intense heat of the corona
of about 1,000,000°C
(1,800,000°F) to 2,000,000°C (3,600,000°F) accelerates
the plasma. to escape velocity. A million tons of
matter are hurled into space every second at an average
speed of 400 km/s ("900,000
miles/hr). Extreme speeds vary from 300 km/s ("700,000 miles/hr)
to 900 km/s ("2 million miles/hr). In the process the plasma drags the
magnetic field lines of the Sun out into space. A
million tons of matter per second is huge. However,
since this solar wind is spread throughout space
in all directions, there are only about 6 protons
per cubic centimeter when the solar wind reaches
Earth. The Ulysses spacecraft
and the Advanced Composition Explorer (ACE)
have gathered considerable information about the
solar wind. Would you like to know the solar wind
conditions for the past seven days? +
Website with forcast
Solar winds are comparable to daily
breezes on Earth -mild and steady. Solar flares,
however, are like intense storms. The solar flares
are much more powerful than solar winds, but they are
localized and tend to blast material in just one direction.
Flares release a quick burst of energy equivalent to
10 million volcanic eruptions or more than a billion
hydrogen bombs. A coronal mass ejection (CME) is the
like a hurricane- an energetic storm spread over a
large area. A CME is the eruption of a huge bubble
of plasma from the corona.
A CME usually travels between 400 km/s (1 million
miles per hour) and 1000 km/s (2 million miles per
hour). A typical eruption can carry a billion tons
of plasma, a mass equal to that of 10,000 aircraft carriers. A
CME is very directional, blasting material out in a
fairly narrow jet that can expand to about 30 million
miles.
Photo Right: Courtesy
of SOHO/LASCO consortium. SOHO is a project
of internatinonal cooperation between ESA and NASA.
Coronal mass ejections occur only
about twice a week when sunspots are at a minimum. However, they
occur as often as 4 to 5 times a day when sunspot activity reaches
its maximum. CMEs are randomly distributed across the surface of
the Sun. Therefore, very few are aimed at Earth. Most of the energy
of a CME that does arrive at Earth is deflected by The
Earth's Magnetosphere. The energy from a CME directed at Earth
can create auroras,
damage satellites, disrupt
radio communication, burn out power transformers and corrode pipelines.
On the relatively unprotected surface of the Moon, these high-energy
protons could easily kill a human. The series of images above show
CMEs that are projected to the side of the Sun as we look at it.
CMEs that are directed at Earth can affect the instruments of satellites,
causing temporary instrument malfunctions and computer shutdowns.
In a few instances satellites were disabled. To observe the CMEs
directed at the Earth in more detail, the STEREO
(Solar Terrestrial Relations Observatory) mission is planned
for launch in 2005. It will observe CMEs directed at the Earth by
placing two spacecraft in a solar orbit identical to Earth's orbit.
One spacecraft will precede the Earth and the other will follow.
Coronal mass ejections aimed at the Earth will be measured in stereo
revealing unprecedented three-dimensional structures of the CME.
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