Space
New Third Radiation Belt Around Earth Revealed by NASA's Van Allen Probe
Mark Hoffman
First Posted: Mar 01, 2013 01:58 AM EST
NASA's Van Allen Probes mission has discovered a previously unknown third radiation belt around Earth, revealing the existence of unexpected structures and processes within these hazardous regions of space.
Previous observations of Earth's Van Allen belts have long documented two distinct regions of trapped radiation surrounding our planet. Particle detection instruments aboard the twin Van Allen Probes, launched last August, quickly revealed to scientists the existence of this new, transient, third radiation belt.
The Van Allen belts are two donut-shaped regions of high-energy particles trapped by Earth's magnetic field. At the time of their discovery in 1958, they were thought to be relatively stable structures, but subsequent observations have shown they are dynamic and mysterious. However, this type of dynamic three-belt structure was never seen, or even considered, theoretically.
The belts, named for their discoverer, James Van Allen, are critical regions for modern society, which is dependent on many space-based technologies. The Van Allen belts are affected by solar storms and space weather and can swell dramatically. When this occurs, they can pose dangers to communications and GPS satellites, as well as humans in space.
"The fantastic new capabilities and advances in technology in the Van Allen Probes have allowed scientists to see in unprecedented detail how the radiation belts are populated with charged particles and will provide insight on what causes them to change, and how these processes affect the upper reaches of Earth's atmosphere," said John Grunsfeld, NASA's associate administrator for science in Washington.
This discovery shows the dynamic and variable nature of the radiation belts and improves our understanding of how they respond to solar activity. The findings, published Thursday in the journal Science, are the result of data gathered by the first dual-spacecraft mission to fly through our planet's radiation belts.
The new high-resolution observations by the Relativistic Electron Proton Telescope (REPT) instrument revealed there can be three distinct, long-lasting belt structures with the emergence of a second empty slot region, or space, in between.
"This is the first time we have had such high-resolution instruments look at time, space and energy together in the outer belt," said Daniel Baker, lead author of the study and REPT instrument lead at the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado in Boulder. "Previous observations of the outer radiation belt only resolved it as a single blurry element. When we turned REPT on just two days after launch, a powerful electron acceleration event was already in progress, and we clearly saw the new belt and new slot between it and the outer belt."
This fast and surprising observation was actually made due to the lucky last minute change of plans proposed by a group of scientists on the mission. They asked that the Relativistic Electron Proton Telescope (REPT) be turned on early - just three days after launch -- in order that its observations would overlap with another mission called SAMPEX (Solar, Anomalous, and Magnetospheric Particle Explorer), that was soon going to de-orbit and re-enter Earth's atmosphere.
It was a lucky decision because shortly before REPT turned on, solar activity on the sun had sent energy toward Earth that caused the radiation belts to swell. The REPT instrument worked well from the moment it was turned on Sep. 1. It made observations of these new particles trapped in the belts, recording their high energies, and the belts' increased size.
Then something happened no one had ever seen before: the particles settled into a new configuration, showing an extra, third belt extending out into space. Within mere days of launch, the Van Allen Probes showed scientists something that would require rewriting textbooks.
Scientists observed the third belt for four weeks before a powerful interplanetary shock wave from the sun annihilated it.
Each Van Allen Probe carries an identical set of five instrument suites that allow scientists to gather data on the belts in unprecedented detail. The data are important for the study of the effect of space weather on Earth, as well as fundamental physical processes observed around other objects, such as planets in our solar system and distant nebulae.
"Even 55 years after their discovery, the Earth's radiation belts still are capable of surprising us and still have mysteries to discover and explain," said Nicky Fox, Van Allen Probes deputy project scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "We thought we knew the radiation belts, but we don't. The advances in technology and detection made by NASA in this mission already have had an almost immediate impact on basic science."
The Van Allen Probes are the second mission in NASA's Living With a Star Program to explore aspects of the connected sun-Earth system that directly affect life and society.
See Now:
NASA's Juno Spacecraft's Rendezvous With Jupiter's Mammoth Cyclone
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First Posted: Mar 01, 2013 01:58 AM EST
NASA's Van Allen Probes mission has discovered a previously unknown third radiation belt around Earth, revealing the existence of unexpected structures and processes within these hazardous regions of space.
Previous observations of Earth's Van Allen belts have long documented two distinct regions of trapped radiation surrounding our planet. Particle detection instruments aboard the twin Van Allen Probes, launched last August, quickly revealed to scientists the existence of this new, transient, third radiation belt.
The Van Allen belts are two donut-shaped regions of high-energy particles trapped by Earth's magnetic field. At the time of their discovery in 1958, they were thought to be relatively stable structures, but subsequent observations have shown they are dynamic and mysterious. However, this type of dynamic three-belt structure was never seen, or even considered, theoretically.
The belts, named for their discoverer, James Van Allen, are critical regions for modern society, which is dependent on many space-based technologies. The Van Allen belts are affected by solar storms and space weather and can swell dramatically. When this occurs, they can pose dangers to communications and GPS satellites, as well as humans in space.
"The fantastic new capabilities and advances in technology in the Van Allen Probes have allowed scientists to see in unprecedented detail how the radiation belts are populated with charged particles and will provide insight on what causes them to change, and how these processes affect the upper reaches of Earth's atmosphere," said John Grunsfeld, NASA's associate administrator for science in Washington.
This discovery shows the dynamic and variable nature of the radiation belts and improves our understanding of how they respond to solar activity. The findings, published Thursday in the journal Science, are the result of data gathered by the first dual-spacecraft mission to fly through our planet's radiation belts.
The new high-resolution observations by the Relativistic Electron Proton Telescope (REPT) instrument revealed there can be three distinct, long-lasting belt structures with the emergence of a second empty slot region, or space, in between.
"This is the first time we have had such high-resolution instruments look at time, space and energy together in the outer belt," said Daniel Baker, lead author of the study and REPT instrument lead at the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado in Boulder. "Previous observations of the outer radiation belt only resolved it as a single blurry element. When we turned REPT on just two days after launch, a powerful electron acceleration event was already in progress, and we clearly saw the new belt and new slot between it and the outer belt."
This fast and surprising observation was actually made due to the lucky last minute change of plans proposed by a group of scientists on the mission. They asked that the Relativistic Electron Proton Telescope (REPT) be turned on early - just three days after launch -- in order that its observations would overlap with another mission called SAMPEX (Solar, Anomalous, and Magnetospheric Particle Explorer), that was soon going to de-orbit and re-enter Earth's atmosphere.
It was a lucky decision because shortly before REPT turned on, solar activity on the sun had sent energy toward Earth that caused the radiation belts to swell. The REPT instrument worked well from the moment it was turned on Sep. 1. It made observations of these new particles trapped in the belts, recording their high energies, and the belts' increased size.
Then something happened no one had ever seen before: the particles settled into a new configuration, showing an extra, third belt extending out into space. Within mere days of launch, the Van Allen Probes showed scientists something that would require rewriting textbooks.
Scientists observed the third belt for four weeks before a powerful interplanetary shock wave from the sun annihilated it.
Each Van Allen Probe carries an identical set of five instrument suites that allow scientists to gather data on the belts in unprecedented detail. The data are important for the study of the effect of space weather on Earth, as well as fundamental physical processes observed around other objects, such as planets in our solar system and distant nebulae.
"Even 55 years after their discovery, the Earth's radiation belts still are capable of surprising us and still have mysteries to discover and explain," said Nicky Fox, Van Allen Probes deputy project scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "We thought we knew the radiation belts, but we don't. The advances in technology and detection made by NASA in this mission already have had an almost immediate impact on basic science."
The Van Allen Probes are the second mission in NASA's Living With a Star Program to explore aspects of the connected sun-Earth system that directly affect life and society.
See Now: NASA's Juno Spacecraft's Rendezvous With Jupiter's Mammoth Cyclone