Who is afraid of solar flares?

[Frutty Profile]

October 7, 2005: Last month, the sun went haywire. Almost every day for two weeks in early September, solar flares issued from a giant sunspot named "active region 798/808." X-rays ionized Earth’s upper atmosphere. Solar protons peppered the Moon. It was not a good time to be in space.

Or was it?

During the storms, something strange happened onboard the International Space Station (ISS): radiation levels dropped.

"The crew of the ISS absorbed about 30% fewer cosmic rays than usual," says Frank Cucinotta, NASA's chief radiation health officer at the Johnson Space Center. "The storms actually improved the radiation environment inside the station."



The International Space Station (ISS).

Scientists have long known about this phenomenon. It's called a "Forbush decrease," after American physicist Scott E. Forbush, who studied cosmic rays in the 1930s and 40s. When cosmic rays hit Earth's upper atmosphere, they produce a shower of secondary particles that can reach the ground. By monitoring these showers he noticed, contrary to intuition, that cosmic ray doses dropped when solar activity was high.


The reason is simple: When sunspots explode, they often hurl massive clouds of hot gas away from the sun. These clouds, called CMEs (coronal mass ejections), contain not only gas but also magnetic force fields, knots of magnetism ripped away from the sun by the explosion. Magnetic fields deflect charged particles, so when a CME sweeps past Earth, it also sweeps away many of the electrically-charged cosmic rays that would otherwise strike our planet. This is the "Forbush decrease."



Wherever CMEs go, cosmic rays are deflected. Forbush decreases have been observed on Earth and in Earth orbit onboard Mir and the ISS. The Pioneer 10 and 11 and Voyager 1 and 2 spacecraft have experienced them, too, beyond the orbit of Neptune.

A single CME can suppress cosmic rays for a few weeks. Sustained solar activity can suppress them for a much longer time: "2005 has been a surprisingly active year on the sun," notes Cucinotta. Since January, astronomers have counted 14 powerful X-class solar flares and an even greater number of CMEs. As a result, "the crew of the ISS has absorbed fewer cosmic rays all year long."

So as you see, there's nothing to worry about. Thanks to the FORBUSH DECREASE!!!!

http://science.nasa.gov/science-news/sc ... ct_afraid/