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Radiation Concentrates During Solar Storms .
Scientists were surprised to learn that the Earth's magnetic field can concentrate radiation from the Sun during powerful solar storms, even in places that were previously thought to be safe. One region is the gap between the two Van Allen radiation belts that surround our planet, which resemble two donuts, one inside the other. In between these belts is a relatively safe area that could be prime real estate for satellites because of the low radiation levels. During the extreme solar weather last year, that safe zone actually filled up with radiation and became quite hazardous for more than five weeks.
The beauty of science is that nothing is for certain. There are times when scientists think they have something figured out and then nature throws them for a loop. Just such an event happened last fall when the Sun erupted in some massive, record-shattering explosions that hurled billion of tons of electrified gas toward Earth.
Scientists realize that space is dangerous for unprotected satellites and astronauts, but they thought that they had found a small safe zone around Earth's radiation belt - a shelter from these dangerous solar storms. It turns out that when the solar storm is strong enough, even this safe zone can become a major hot zone for dangerous radiation.
"Space weather matters - we now know that no matter what orbit we choose, there is the possibility that a spacecraft could get blasted by a significant dose of radiation. We need to take this into account when designing spacecraft. We also need to the ability to continuously monitor space weather so satellite operators can take protective measures during solar storms," said Dr. Daniel Baker, Director of the Laboratory for Atmospheric and Space physics at the University of Colorado, Boulder.
The region is more of a gap between the two Van Allen radiation belts that surround Earth. The two belts resemble one donut inside the other. The belts are comprised of high-speed electrically charged particles trapped in the Earth's magnetic field. It can almost be thought of as a giant umbrella in space shielding Earth from these space events.
The safe zone is considered prime real estate for satellites in "middle Earth orbits" because they would be exposed to relatively small doses of radiation and cost less to build. While there are currently no satellites in that particular orbit, many are being seriously considered including some from the Air Force.
To call the Sun active in late October / early November is an understatement. Within a two-week period, the Sun released an unusually high number of coronal mass ejections (CMEs) into space, and experienced explosions many times more powerful than anything ever observed. For some perspective, flares are usually ranked by number and class. A large flare might be X-2, for example. The Nov. 4 flare was ranked X-28, although more precisely, "off the scale" because it was hard to get an exact measurement. To add to the drama, the Sun is headed into its period of minimum activity within its 11-year cycle, making the number and intensity of the fall flares unusually high. The maximum and most active period occurred around 2000-2001.
Fortunately the science community has a number of satellites to track solar comings and goings. The Solar, Anomalous and Magnetospheric Particle Explorer (SAMPEX) satellite flies through the Van Allen radiation belts, taking measurements of the particle types and their energy and abundance. It observed the formation of a new belt in the safe zone on Oct. 31, 2003. That new belt made the safe zone hazardous for more than five weeks until the radiation was able to drain away and be absorbed by our Earth's atmosphere. Other satellites helped researchers track the solar storms as they generated auroras on Earth, and spread out to Mars, Jupiter, Saturn, and the very edges of the solar system.
"This was an extreme event, a natural experiment that will be used to better understand how radiation belts work," summed up Dr. Baker. "We were fortunate to have a suite of spacecraft in place to observe this event. This is why it's important to systematically and continuously observe space weather, because there is always the potential to be surprised by nature."
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