2005
24 May 2005. Solar
Fireworks Signal New Space Weather Mystery.
NASA RELEASE 05-132. The
most intense burst of solar radiation in five
decades accompanied a large solar flare on
January 20. It shook space weather theory
and highlighted the need for new forecasting
techniques, according to several presentations
at the American Geophysical Union (AGU) meeting
this week in New Orleans. The solar flare,
which occurred at 2 a.m. EST, tripped radiation
monitors all over the planet and scrambled
detectors on spacecraft. The shower of energetic
protons came minutes after the first sign
of the flare. This flare was an extreme example
of the type of radiation storm that arrives
too quickly to warn interplanetary astronauts. "This
flare produced the largest solar radiation
signal on the ground in nearly 50 years," said
Dr. Richard Mewaldt of the California Institute
of Technology, Pasadena, Calif. ... "But
we were really surprised when we saw how fast
the particles reached their peak intensity
and arrived at Earth." Normally it takes
two or more hours for a dangerous proton shower
to reach maximum intensity at Earth after
a solar flare. The particles from the January
20 flare peaked about 15 minutes after the
first sign. ...The Transitional Region and
Coronal Explorer (TRACE) ... has identified
a possible source of the magnetic stress that
causes solar flares. The sunspots that give
off the very largest (X-class) flares appear
to rotate in the days around the flare.
"This rotation stretches and
twists the magnetic field lines
over the sunspots", Nightingale
said.
"We have seen it before virtually
every X-flare that TRACE has observed
since it was launched and more
than half of all flares in that
time." However, rotating sunspots
are not the whole story. The unique
flare came at the end of a string
of five other very large flares
from the same sunspot group, and
no one knows why this one produced
more sudden high energy particles
than the first four. "It means
we really don't understand how
the sun works," Lin said.
"We need to continue to operate
and exploit our fleet of solar-observing
spacecraft to identify how it works." |
