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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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