August 26th, 2012 by James Ayre
The launch of NASA’s radiation belt probes has been delayed from its early Friday (Aug. 23) launch date because of Tropical Storm Isaac. The next launch attempt will be made on August 30th according to the United Launch Alliance.
The radiation belt probes will conduct a mission to explore some of the “harshest, most hazardous regions of space, the Van Allen Belts.”
The existence of the radiation belts has been known of by researchers for at least half a century, but not much is really known about them.
“Extending up to 25,000 miles (40,000 kilometers) around the Earth like a giant doughnut, the Van Allen Belts contain highly energized particles capable of penetrating metallic satellites — or the softer human tissue of astronauts in space.”
“Ejections from the sun —dangerous enough on their own — can create a shockwave that bends the radiation belts toward Earth, accelerating quick-moving particles even faster. The resulting onslaught can damage power grids, disrupt satellites and GPS and threaten passengers aboard high-flying planes.”
“The $686 million Radiation Belt Storm Probes (RBSP) mission will help scientists to understand more about the chaotic regions overhead. The invisible particles within the belts make even determining their shifting size a challenge.”
“In order to measure them, you have to fly through them with sensitive instruments,” said Berry Mauk, RBSP project scientist.
“However, radiation levels within the belts are constantly changing, and scientists aren’t completely certain of why.”
“If you can’t answer simple questions, you can’t even begin to hypothesize why that radiation suddenly went up,” Mauk said.
“Most of the particles trapped in the Van Allen Belts stream in from the sun, though some come from cosmic rays in space. Bouts of high solar activity can accelerate or boost the contents of the radiation belts, but similar events don’t always cause the same reaction.”
“A coronal mass ejection — a large, fast-moving collection of particles shot from the sun toward Earth — might cause phenomenal auroras and damage power transistors one day, while a similar assault months later might have only minimal effects.”
“The reason for the differences isn’t clear, but it’s one question that RSBP hopes to find some answers to. To do so, the two crafts will travel to the heart of the radiation belts to study how the various types of particles are distributed.”
“The belts contain electrons and protons at various energy levels, as well as heavier particles of ionized oxygen and helium. Hot plasma also surrounds the Earth, ionized gas that puts out only a few tens of volts. The plasma travels in waves, and when it encounters the other particles, it affects their motion.”
“Think about plasma waves like sound waves in the atmosphere,” Mauk said.
“Those plasma waves exchange energy with very high-energy radiation particles.”
“Some of the particles are accelerated by their contact with the plasma, while others lose energy.”
“RBSP also intends to study how the different particles move through the space around Earth. As they stream from the sun into the Van Allen Belts, they get caught by the magnetic field lines and begin to spiral around them, accelerating.”
“But the belts don’t capture all of the particles. Some hit the field lines at just the right angle, rebounding into space or into the Earth’s atmosphere in what scientists call ‘bounce motion.’ Other particles may drift around the Earth itself, moving from the day to night side. The higher energy particles move faster than their lower energy cousins, making it possible to reconstruct the event that originally energized the particles.”
“It’s a very complicated interchange between low-energy, medium-energy and high-energy particles, and we have to measure all of those,” Mauk.
“Earth isn’t the only planet in the solar system with radiation belts. Though very different, both Jupiter and Saturn boast bands of charged particles around them. And X-ray and radio astronomy missions record high radiation regions all over the universe, in places such as the Crab Nebula. So in addition to helping protect astronauts, satellites and sensitive electronics, RBSP can also lend insight into more distant locations.”
“We’re using Earth’s radiation belt as a natural laboratory here so we can understand the creation of radiation regions elsewhere in the solar system, and elsewhere in the universe,” Mauk said.
Image Credits: NASA/T. Benesch, J. Carns; United Launch Alliance/Pat Corkery
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