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Escape of the Destructive Electrons - Presented by Science@NASA.
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Warning, Earth is surrounded by electrons that can be disruptive to our technology.
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A population of high energy electrons inhabits the Van Allen radiation belts, high above Earth.
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While these electrons pose no danger to humans on Earth's surface, where we're protected by the atmosphere, they have been blamed for many spacecraft failures.
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Electron swarms can penetrate and electrify the hulls of satellites, and short-circuit sensitive electronics.
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Avoiding them is a good idea. To avoid them, though you have to figure out where they are, and that's a problem because these electrons can be very elusive.
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The Van Allen belts were discovered in 1958, and their discovery was one of the earliest scientific achievements of the space age.
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During solar storms, high energy electrons in the belts have been known to vanish, only to return a few hours later.
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This strange phenomenon was first spotted in the 1960s, and it has puzzled physicists ever since.
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In 2012, NASA launched the Radiation Belt Storm Probes or RBSP, which have since been renamed the Van Allen probes.
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Rather than avoiding the radiation belts, these heavily shielded spacecraft regularly fly right into them.
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Their mission is to discover what makes the belt so dangerous, and moreover, so unpredictable.
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In a few years since they have launched, the Van Allen probes have made many discoveries, such as the occasional existence of a third radiation belt that no one knew about before.
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The mystery of the vanishing electrons, however, has not been fully solved.
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A popular idea among researchers is that the electrons precipitate into Earth's upper atmosphere, depositing their energy high above our planet's surface.
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But how? What could trigger such an electron rainfall?
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To answer this question, the Van Allen probes needed help from below.
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Since 2013 an international team of researchers, led by physicist Robyn Millan of Dartmouth College, have been launching research balloons from Antarctica, each standing more than eight stories tall.
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These mammoth balloons ride circumpolar winds around the South Pole,
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floating as much as 40 kilometers high, as they look for signs that electrons are penetrating the atmosphere overhead.
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The name of the program is BARREL, short for Balloon Array for Radiation Belt Relativistic Electron Losses.
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The electron rainfall, when it occurs, reveals itself by telltale glow of x-rays.
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These X-Rays are the byproduct of electrons striking atoms and molecules in the upper atmosphere.
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BARREL's balloons are equipped with a payload of sensors to observe such emissions.
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Occasionally the balloons are in flight when the Van Allen probes pass overhead.
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Such a conjunction is perfect for this research, the two probes can track the electrons from above, while the balloons do so from below.
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There were two such conjunctions, one on January 3rd and another on January 6th, 2014 and researchers put them to good use.
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Working together, the Van Allen probes and BARREL were able to piece together a means of escape.
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"Electrons were gradually eroded away over the course of several days, in part by interaction with plasmaspheric hiss," wrote Millan and colleagues in a letter published to Nature.
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Plasmaspheric hiss is a type of electromagnetic radiation, or plasma wave, that can scatter these high energy electrons down toward earth.
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Looking up from Antarctica, BARREL could measure the electrons losing their energy in the form of relatively harmless x-rays.
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Plasmaspheric hiss was simultaneously observed by both Van Allen probes satellites.
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There may be other ways for the electrons to escape the Van Allen belts, so the mystery is not fully solved.
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As 2015 is coming to an end, the BARREL team has completed a third campaign of balloon flights over Sweden in search of more clues.
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Stay tuned for updates from science.nasa.gov.