We may have accidentally formed a protective bubble around Earth
The discovery comes from the Van Allen Probes—two spacecraft, launched in 2012, that patrol the radiation belts surrounding Earth. The Van Allen radiation belts are zones where charged particles streaming from the sun get stuck in Earth’s magnetic field. These high energy protons and electrons can destroy a satellite’s electronics, which is a constant concern because the belts don’t always stay in one place.
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During an intense geomagnetic storm in 2015, a large solar storm knocked back the plasmasphere, but surprisingly the outer Van Allen belt didn’t come any closer to Earth. “The plasma retracted but the belt didn’t follow,” says Erickson. But he and his colleagues noticed something else: “The edge of where these very powerful radio signals stop is the same place where the electrons stop coming in.”
In addition, data from the 1960s suggests that the belt’s inner boundary was much closer to Earth back when VLF transmissions were less common. The team thinks that, nowadays, when electrons shooting out from a solar storm approach Earth, VLF waves deflect them, knocking them off their trajectory and pushing them into the atmosphere, where they get lost.
What bizarre alien planet is this? It’s planet Earth of course, seen from the International Space Station through the shimmering glow of aurorae. About 400 kilometers (250 miles) above Earth, the orbiting station is itself within the upper realm of the auroral displays. Aurorae have the signature colors of excited molecules and atoms at the low densities found at extreme altitudes. Emission from atomic oxygen dominates this view. The eerie glow is green at lower altitudes, but a rarer reddish band extends above the space station’s horizon.
This animation of Jupiter is made from more than 1,000 images taken by 91 amateurs from around the world between the 19th of December 2014 and the 31st of March 2015.
A photo of Saturn and Titan crossing the galactic plane near the galactic center, taken by astrophotographer Damian Peach on May 2, 2017.
Animation of raw (uncalibrated) images captured by @CassiniSaturn during its outbound portion of ring dive #2 on May 3 #CassiniInspires pic.twitter.com/zNtMBSpfyr
— Jason Major (@JPMajor)May 4, 2017
Cassini Finds ‘The Big Empty’ Close to Saturn
As NASA’s Cassini spacecraft prepares to shoot the narrow gap between Saturn and its rings for the second time in its Grand Finale, Cassini engineers are delighted, while ring scientists are puzzled, that the region appears to be relatively dust-free. This assessment is based on data Cassini collected during its first dive through the region on April 26.
With this information in hand, the Cassini team will now move forward with its preferred plan of science observations.
“The region between the rings and Saturn is 'the big empty,’ apparently,” said Cassini Project Manager Earl Maize of NASA’s Jet Propulsion Laboratory in Pasadena, California. “Cassini will stay the course, while the scientists work on the mystery of why the dust level is much lower than expected.”
A dustier environment in the gap might have meant the spacecraft’s saucer-shaped main antenna would be needed as a shield during most future dives through the ring plane. This would have forced changes to how and when Cassini’s instruments would be able to make observations. Fortunately, it appears that the “plan B” option is no longer needed. (There are 21 dives remaining. Four of them pass through the innermost fringes of Saturn’s rings, necessitating that the antenna be used as a shield on those orbits.)
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