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Solar Storms: Fast Facts

This story is a supplement to the feature "Bracing the Satellite Infrastructure for a Solar Superstorm" which was printed in the August 2008 issue of Scientific American.

It’s Raining Protons
Like terrestrial hurricanes and thunderstorms, solar storms can wreak havoc in multiple ways.

  • Solar flares are relatively small-scale explosions that emit bursts of radiation. They cause enhanced radio absorption in the so-called D layer of Earth’s ionosphere, interfering with Global Positioning System signals and shortwave reception. Flares also heat the upper atmosphere, puffing it up and increasing drag on satellites.
  • Coronal mass ejections (CMEs) are giant bubbles of ionized gas. If Earth is caught in their crosshairs, they can induce electric currents that surge into pipelines, cables and electrical transformers.
  • Solar proton events are floods of high-energy protons that occasionally accompany flares and CMEs. They can zap data in electronic circuits and give astronauts and airline passengers an extra dose of radiation.

Zapping Your Computer
A superstorm might well have strange effects on electronics. The high-energy protons that reach the ground produce neutrons that pass right through the shielding around satellite and avionics systems. (Most computer systems lack even this shielding.)

Extensive background radiation studies by IBM in the 1990s suggest that computers typically experience about one cosmic-ray-induced error per 256 megabytes of RAM per month. If so, a superstorm, with its unprecedented radiation fluxes, could cause widespread computer failures. For­tun­ately, in such instances most users could simply reboot.

Would Astronauts Get Fried?
One piece of good news about superstorms is that the radiation dosage to astronauts in low-Earth orbit would probably not be life-threatening. Lawrence W. Townsend of the University of Tennessee calculated a superstorm dose of about 20 rads (0.2 gray), which is comparable to the 30-day cumulative exposure limits set by NASA.

On the other hand, this one-time event would still be more radiation than someone living on the ground would receive from natural environmental sources over the course of 70 years. Airline passengers might receive a dose equal to a CT scan.

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