NASA Discovers New Radiation Belt Around Earth

Two giant swaths of radiation, known as the Van Allen Belts, surrounding Earth were discovered in 1958. 

In 2012, observations from the Van Allen Probes showed that a third belt can sometimes appear.

The radiation is shown here in yellow, with green representing the spaces between the belts.

CREDIT: NASA/Van Allen Probes/Goddard Space Flight Center

A ring of radiation previously unknown to science fleetingly surrounded Earth last year before being virtually annihilated by a powerful interplanetary shock wave, scientists say.

NASA's twin Van Allen space probes, which are studying the Earth's radiation belts, made the cosmic find. The surprising discovery — a new, albeit temporary, radiation belt around Earth — reveals how much remains unknown about outer space, even those regions closest to the planet, researchers added.


After humanity began exploring space, the first major find made there were the Van Allen radiation belts, zones of magnetically trapped, highly energetic charged particles first discovered in 1958.

"They were something we thought we mostly understood by now, the first discovery of the Space Age," said lead study author Daniel Baker, a space scientist at the University of Colorado.

These belts were believed to consist of two rings: an inner zone made up of both high-energy electrons and very energetic positive ions that remains stable in intensity over the course of years to decades; and an outer zone comprised mostly of high-energy electrons whose intensity swings over the course of hours to days depending primarily on the influence from the solar wind, the flood of radiation streaming from the sun.

The discovery of a temporary new radiation belt now has scientists reviewing the Van Allen radiation belt models to understand how it occurred.

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. 

CREDIT: NASA/SDO/AIA/Goddard Space Flight Center

The giant amounts of radiation the Van Allen belts generate can pose serious risks for satellites. To learn more about them, NASA launched twin spacecraft (RBSP), the Van Allen probes, in the summer of 2012.

The RBSP satellites were armed with a host of sensors to thoroughly analyze the plasma, energetic particles, magnetic fields and plasma waves in these belts with unprecedented sensitivity and resolution.


The identical Radiation Belt Storm Probes (RBSP) will follow similar orbits that will take them through both the inner and outer radiation belts. 

The highly elliptical orbits range from a minimum altitude of approximately 373 miles (600 kilometers) to a maximum altitude of approximately 23,000 miles (37,000 kilometers). 

CREDIT: JHU/APL, NASA

It remains uncertain how this temporary radiation belt arose. Van Allen mission scientists suspect it was likely created by the solar wind tearing away the outer Van Allen belt.

"It looks like its existence may have been bookended by solar disturbances," Baker said.

Future study of the Van Allen belts can reveal if such temporary rings of radiation are common or rare.

"Do these occur frequently, or did we get lucky and see a very rare circumstance that happens only once in a while?" Baker said. "And what other unusual revelations might come now that we are really looking at these radiation belts with new, modern tools?"

The scientists detailed their findings online Feb. 28 in the journal Science.