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Van Allen Probes Discover New Radiation Belt, Possibly Due To Solar Storm

February 28, 2013
Image Caption: On Aug. 31, 2012, a giant prominence on the sun erupted, sending out particles and a shock wave that traveled near Earth. This event may have been one of the causes of a third radiation belt that appeared around Earth a few days later, a phenomenon that was observed for the very first time by the newly-launched Van Allen Probes. This image of the prominence before it erupted was captured by NASA's Solar Dynamics Observatory (SDO). Credit: NASA/SDO/AIA/Goddard Space Flight Center.

Lee Rannals for redOrbit.com — Your Universe Online

NASA announced that its Van Allen Probes have led to a revision of a 50-year-old theory about the Earth’s radiation belts.

The Van Allen radiation belts surrounding Earth were thought to be just two giant swaths of radiation, first discovered in 1958. More than a half-century later, NASA launched twin probes (August 30, 2012) to create a detailed map of the region and catalogue a variety of energies and particles in these radiation belts.

Each Van Allen Probe orbiting around our planet contains a Relativistic Eletron-Proton Telescope (REPT) designed by scientists from University of Colorado’s Laboratory for Atmospheric and Space Physics (LASP). Just a few days after the scientists turned on the instruments, they began to see the formation of a third “storage ring” radiation belt.

“It was so odd looking, I thought there must be something wrong with the instrument,” said LASP Director Dan Baker, REPT principal investigator and lead author of the study published online today in the journal Science. “But we saw things identically on each of the spacecraft. We had to come to the conclusion that this was real.”

Shri Kanekal, the deputy mission scientist for the Van Allen Probes at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said that by the fifth day, they were able to plot observations and watch the formation of a third radiation belt.

“We started wondering if there was something wrong with our instruments. We checked everything, but there was nothing wrong with them. The third belt persisted beautifully, day after day, week after week, for four weeks,” Kanekal added.

Data sent back to Earth during September initially showed two Van Allen belts, which is what scientists had expected to see. However a few days later, a third belt of electrons began to form farther out from the other two rings. Scientists say the middle “storage ring” persisted as the belt farthest away from Earth, but it began to decay away in the third week of September, until an interplanetary shockwave traveling from the sun destroyed both it and the rest of the outer belt.

The outer Van Allen Belt has been known to fluctuate and at times swell with charged particles. In the months since the first two belts virtually disappeared, the Van Allen radiation zones re-formed into the original two-belt structure.

“We have no idea how often this sort of thing happens,” Baker said. “This may occur fairly frequently but we didn’t have the tools to see it.”

This new configuration could offer scientists new clues to what causes the changing shapes of the belts. The Van Allen belt region can swell dramatically in response to incoming energy from the sun, which is also known as space weather.

NASA said the Van Allen Probes have worked well for their first six months, and scientists are excited about data that continues to stream in with unprecedented clarity. Scientists still do not have a complete understanding about the belts, despite knowing about their existence for some 55 years.

“I consider ourselves very fortunate (sic),” says Baker. “By turning on our instruments when we did, taking great pride in our engineers and having confidence that the instruments would work immediately and having the cooperation of the sun to drive the system the way it did — it was an extraordinary opportunity. It validates the importance of this mission and how important it is to revisit the Van Allen Belts with new eyes.”

The Van Allen Probes were originally named the Radiation Belt Storm Probes (RBSP). However, NASA decided to rename the probes back in November in honor of the late James Van Allen, who first discovered the belts in 1958.

“James Van Allen was a true pioneer in astrophysics,” said John Grunsfeld, astronaut and associate administrator for NASA´s Science Mission Directorate at the agency´s headquarters in Washington. “His ground breaking research paved the way for current and future space exploration. These spacecraft now not only honor his iconic name but his mark on science.”


Source: Lee Rannals for redOrbit.com – Your Universe Online



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