Friedberg has a short flight scheduled himself this weekend. "If I was going today, I would go," he said. "But I'm not pregnant."
High-frequency radio communications will also be strongly affected through Sunday, when the proton stream is expected to die down.
Effect on space travelers
The proton stream is
[quote]
The portable device, similar to those used during each space shuttle mission, will sound an alarm if it senses radiation that reaches a preset level, said NASA spokesman Rob Navias.
If that should happen, the three crew members will move to the end of the Zvezda service module
and remain there until the radiation level subsides. This part of Space Station Alpha offers the most protection from the hazard, Navias said.
In any case there is no need for Shepherd, Gidzenko and Krikalev to move into the Soyuz for protection, nor are there any plans for the crew to evacuate the station and return to Earth.
"This particular solar flare, even if it reaches the levels that would trigger that alarm on board, would have no impact to crew health, or crew safety," Navias said.
But the long-term effects of exposure to cosmic radiation and solar storms are more worrisome, and not entirely known.
NASA keeps an eye on the amount of radiation an astronaut accumulates during several missions, and once they hit their limit they can't fly anymore. What that limit is depends on each crew member, and because of medical privacy it's never been publicly announced that an astronaut won't fly because of radiation concerns.
Airline passenger threat
Scientists have known for nearly a century that the effects of radiation increase with altitude.
There is debate over how much danger an event of this type poses to airline passengers. But experts agree that any potential danger depends on the route of the plane.
"If you fly from Philadelphia to Atlanta, it probably isn't going to have any effect on you," said Kunches, the NOAA forecaster. "Flights in the polar regions are going to be much more susceptible to seeing some effects."
Other scientists say the amount of radiation in the atmosphere can be twice as much at the poles as elsewhere. This is because Earth's magnetic field channels incoming energy toward the polar regions.
Even on normal flights in non-storm conditions, researchers say the risk to unborn babies might be too great if a pregnant women takes frequent, long flights.
Northern lights
The solar flare also triggered what scientists call
. Energy from this type of event takes two to three days to reach Earth, and fuels the colorful displays called the northern lights, or aurora borealis. (In the Southern Hemisphere there are southern lights, or the aurora australis.)
On Friday morning, NOAA space weather forecaster Christopher Balch told SPACE.com that the energy from this event began reaching Earth late Thursday -- sooner than expected -- and that there was a chance for a strong aurora display at mid latitudes Friday night.
"But there's a lot of uncertainty," Balch said. "It seems like getting that far south is less likely [than earlier expected]. If we get anything at all, it's going to be more of a high-latitude disturbance."
Either way, he said, the aurora will likely quiet down by Sunday, barring any new solar activity.
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