NASA now aiming to target electric atmosphere

NASA is set to launch a mission next month to study plasma – electrified gas that makes 99 percent of the universe.

Beyond Earth's protective atmosphere and extending all the way through interplanetary space, these electrified particles dominate the scene.

Understanding this environment so foreign to our own is crucial to understanding the make up of every star and galaxy in outer space.

Two giant donuts of this plasma surround Earth, trapped within a region known as the Van Allen Radiation Belts. The belts lie close to Earth, sandwiched between satellites in geostationary orbit above and satellites in low Earth orbit (LEO) are generally below the belts.

The new NASA mission called the Radiation Belt Storm Probes (RBSP), due to launch in August 2012, will improve our understanding of what makes plasma move in and out of these electrified belts wrapped around our planet.

“We discovered the radiation belts in observations from the very first spacecraft, Explorer 1, in 1958,” said David Sibeck, a space scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., and the mission scientist for RBSP.

“Characterizing these belts filled with dangerous particles was a great success of the early space age, but those observations led to as many questions as answers. These are fascinating science questions, but also practical questions, since we need to protect satellites from the radiation in the belts,” Sibeck explained.

Scientists want to understand not only the origins of electrified particles – possibly from the solar wind constantly streaming off the sun; possibly from an area of Earth's own outer atmosphere, the ionosphere – but also what mechanisms gives the particles their extreme speed and energy.

“We know examples where a storm of incoming particles from the sun can cause the two belts to swell so much that they merge and appear to form a single belt,” said Shri Kanekal, RBSP's deputy project scientist at Goddard.

“Then there are other examples where a large storm from the sun didn't affect the belts at all, and even cases where the belts shrank. Since the effects can be so different, there is a joke within the community that 'If you've seen one storm . . . You've seen one storm.' We need to figure out what causes the differences,” he stated.

There are two broad theories on how the particles get energy: from radial transport or in situ. In radial transport, particles move perpendicular to the magnetic fields within the belts from areas of low magnetic strength far from Earth to areas of high magnetic strength nearer Earth. The laws of physics dictate that particle energies correlate to the strength of the magnetic field, increasing as they move towards Earth. The in situ theory posits that electromagnetic waves buffet the particles -- much like regular pushes on a swing -- successively raising their speed (and energy).

As for how the particles leave the belts, scientists again agree on two broad possibilities: particles go up, or they go down. Perhaps they travel down magnetic field lines toward Earth, out of the belts into the ionosphere, where they stay part of Earth's magnetic system with the potential to return to the belts at some point. Or they are transported up and out, on a one-way trip to leave the magnetosphere forever and enter interplanetary space.

“In reality, the final answers may well be a combination of the basic possibilities,” said Sibeck.

“There may be, and probably are, multiple processes at multiple scales at multiple locations. So RBSP will perform very broad measurements and observe numerous attributes of waves and particles to see how each event influences others,” he added.

To distinguish between the wide array of potential theories – not to mention combinations thereof – the instruments on RBSP will be equipped to measure a wide spectrum of information. RBSP will measure a host of different particles, including hydrogen, helium and oxygen, as well as measure magnetic fields and electric fields throughout the belts, both of which can guide the movement of these particles.

RBSP will also measure a wide range of energies from the coldest particles in the ionosphere to the most energetic, most dangerous particles. Information about how the radiation belts swell and shrink will help improve models of Earth's magnetosphere as a whole.