Another strategy would station satellites that emit VLF waves in the radiation belts. “The problem is that you’d need quite a lot of energy,” Bortnik said, and large antennas that would be challenging to fit onto spacecraft.
Still, Bortnik points out, the U.S. Air Force’s Demonstration and Science Experiments (DSX) satellite, set for launch in 2016, will carry an instrument to monitor the effects that VLF waves broadcast in space might have on these dangerous electrons. “Those experiments can show how well VLF waves actually do, and maybe change what we think we know about what is needed to clear away electrons,” Bortnik said.
Initial efforts to clear the Van Allen belts targeted electrons because they tend to get trapped there as the result of high-altitude nuclear explosions. In 1962, a U.S. high-altitude nuclear weapons test named Starfish Prime generated a highly energetic artificial electron belt that disabled the first commercial communications satellite, TelStar 1, so researchers sought ways to protect spacecraft from nuclear weapons used in space.
However, it’s the protons in the inner belt that scientists have recently explored. Getting rid of them would potentially open up valuable new orbits for satellites and make travel safer for astronauts, said Maria de Soria-Santacruz Pich, whose Ph.D. work at MIT was on manipulating the Van Allen belts. It might also be impossible.
“Protons are heavy, about 2,000 times heavier than electrons, so if you imagine a proton bashing into a piece of silicon, it can do a whole lot more damage than an electron,” Bortnik said. “Clearing them out would be good.”
Pich and her colleagues discovered that a type of VLF electromagnetic wave known as an electromagnetic ion cyclotron (EMIC) wave could potentially disperse protons in the inner belt. Pich said this strategy poses no hazard to Earth -- the swarm of protons would be virtually unnoticed in the atmosphere.
Pich and her colleagues recently refined the computational strategy needed to figure out what frequencies space-based antennas should use and how much power is needed. However, Pich also found that to disperse all the protons from the region, you’d need a million 15-meter antennas operating for a few years, “which is indeed not feasible in the near future,” she said.
Nonetheless, Pich noted, her calculations assume that the waves these antennas generate do not bounce back and forth inside the inner belt. If they do, that could greatly improve their effectiveness, potentially making the strategy possible. A satellite mission would decide the matter one way or another, but there’s a lot of engineering work needed to even propose such a mission, she said.
It remains uncertain as to whether removing these radiation belts might have unintended consequences. “At present we don’t think there is any downside to not having them, but as with all things geophysical, it is hard to know all the complex interconnections between the various systems and estimate the full effect of removing the radiation belts completely,” Bortnik said. “That’s the most any of us can really say at the moment.”
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