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Making Models
Scientists can learn a great deal
about how the currents and magnetism on the Sun work as a
system by studying models of the Sun's surface in their laboratories
or in detailed computer calculations. Even though the difference
in size between the Sun's diameter (6.5 x 1010
meters) and a lap top computer (0.3 meters) is enormous (about
2 x 1011 times), many physical laws can be scaled
up or down in size so that even enormous solar flares can
be investigated in human-sized models. Sometimes one group
of sunspots collides with another like ships floating on the
Sun's plasma ocean. Sometimes a brand new sunspot can appear
inside one that was already there. If the magnetic polarities
are the same, nothing much happens. But if they are opposite
each other in some area of the Sun's surface, then this can
only mean one thing: great energy is released as currents
flow to annihilate some of the magnetic field (until a balance
is achieved in which the field becomes simpler).
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close up of a solar flare taken by the SOHO
spacecraft. The scale of the Earth is provided.
(Click
to launch movie.)
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Because sunspots and the gases around them
can flow at thousands of kilometers a minute, it only takes
a few minutes before magnetic conditions can escalate from a
minor solar squall to a major explosion of energy. The billions
of amperes of current moving in opposite directions through
the solar atmosphere release over 1025 Joules of
energy;
more energy than in a billion hydrogen bombs.
Powerful Currents
Within 20 minutes or less of a flare,
the magnetic field of an active region changes into a simpler
arrangement of energy. Meanwhile, gas has been heated to millions
of degrees and a blast of X-rays leaves the scene of the event.
In 9 minutes, the X-rays, traveling at 3 x 105
kilometers/second arrive at Earth, and cause short-wave blackouts
across the entire daytime face of the planet. As the X-rays
reach the daytime side of Earth, they cause major changes
in the upper layers of the atmosphere, especially the ionosphere.
The ionosphere is used in short-wave radio communications
(which bounce transmitted signals off of its lower edge),
and solar flare disturbances can disrupt radio communication
for hours at a time. Any astronaut in space, or sensitive
satellite electronics, can also be damaged by the extra intense
x-rays from flares unless the proper precautions and shielding
are used to reduce their risk.
Find
out more about the Sun-Earth Connection at the Sun-Earth
Connection Education Forum Web site.
Text adapted from the
Sun-Earth Connection Tutorial courtesy of NASA, originally
written by Dr. Sten Odenwald. Images and videos courtesy of
NASA unless otherwised noted.
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