[Wswss] : [VHF] Anatomy of a Solar Storm

[Ralph Bergman]

The worst solar-storm season in half a century starts this year.  These 
fiery explosions-which unleash as much energy as a billion hydrogen  
bombs-could, under the right conditions, black out cities and fry
satellites.  But new 
solar scopes give us advance warning. 

 

by NASA  
_View  Photo Gallery_ 
(http://www.popsci.com/military-aviation-space/gallery/2007-05/solar-stor
m-trackers)  
 
A colossal wave sweeps across the entire solar surface within minutes,  
bulldozing everything in its path. The rare tsunami-like shockwave forms
on the 
heels of a major flare that erupted from an Earth-size sunspot 15 minutes
 
earlier. Though that storm didn't have a major impact on Earth, we aren't

always  so lucky.  

The Earth's magnetic shield protects us from the worst effects of  solar 
storms (and even astronauts on the International Space Station can take 
cover 
in a heavily shielded module), but technology suffers greatly.
Atmospheric  
and magnetic fluctuations that the storms cause can also disable 
satellites,  burn out transformers, and take down power grids. One CME in
1989 left 
all of  Quebec without power for nine hours.  
The frequency and intensity of storms varies depending on the solar
season, 
which waxes and wanes in 11-year cycles. We will soon be entering into a 
new  season of high solar activity, and experts predict-by crunching data
on 
the  long-term behavior of the sun's convection currents-that it will be
the 
stormiest in half a century. 
Though we can't yet predict such storms, it's only a matter of time.  
Space-weather forecasters use _satellites and ground-based  scopes_ 
(http://www.popsci.com/node/2288)  to monitor sunspots for flares and
CMEs but can't tell 
with certainty  if or when they will hit Earth. The STEREO satellites
will 
help scientists  determine whether a particular storm is headed for us
and, 
hopefully, will give  satellite and energy-grid minders enough warning to

prepare for a hit.  
Read on for to learn how solar storms work, then launch the gallery 
_here_ 
(http://www.popsci.com/node/2288)  for a look at the  satellites and 
observatories that are keeping us informed.
 
    1.  Sunspots
 
Sunspots form where intense magnetic  field lines twist and poke up
through 
the surface. These knotted fields shut  down the normal flow, or 
convection, of hot plasma from the sun's interior to  the surface, making
the region 
cooler and darker than its surroundings.  
    2.  Field Lines
 
Sunspots explode when the field lines  twist to the point of snapping,
like 
a rubber band wound too tightly. They  link up again to form a new shape,

but not before releasing enormous amounts  of stored energy and hot gas
into 
the sun's outer atmosphere, or corona.  
    3.  Solar Flare
 
The resulting eruption, called a solar  flare, heats the surrounding gas
to 
180 million degrees Fahrenheit. The  explosion accelerates subatomic 
particles to near light-speed and spews  radiation (mostly ultraviolet
and gamma 
rays and x-rays) into space.  
    4.  Plasma Burst
 
Flares are sometimes followed by  coronal mass ejections (CMEs), in which

billions of tons of the sun's plasma  are flung into space en masse.
These 
huge bubbles of matter travel relatively  slowly (1,000 miles a second);
even 
the fastest ones take a day or so to reach  Earth.  
    5.  Earth Impact
 
Eight minutes after a flare erupts,  Earth's atmosphere absorbs the 
radiation pulse. This pulse produces extra ions  and electrons, causing
the 
atmosphere to puff out. The expanded atmosphere  increases drag on
satellites and 
degrades radio and GPS signals. But the worst  is yet to come.
Potentially 
more destructive than a flare's radiation pulse,  CMEs boost the speed of
the 
solar wind and create a shockwave of energetic  protons. That shockwave 
distorts Earth's magnetic shield, and the protons  stream down on the
poles 
creating geomagnetic disturbances like the Northern  Lights. The
shockwave can 
also destroy the electronics in  satellites.
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