by Mara Johnson-Groh for GSFC News
Greenbelt MD (SPX) Nov 02, 2017
Space may seem empty, but it's actually a dynamic place populated with near-invisible matter, and dominated by forces, in particular those created by magnetic fields. Magnetospheres - the magnetic fields around most planets - exist throughout our solar system. They deflect high-energy, charged particles called cosmic rays that are spewed out by the Sun or come from interstellar space. Along with atmospheres, they happen to protect the planets' surfaces from this harmful radiation.
But not all magnetospheres are created equal: Venus and Mars do not have magnetospheres at all, while the other planets - and one moon - have ones that are surprisingly different.
NASA has launched a fleet of missions to study the planets in our solar system - many of which have sent back crucial information about magnetospheres. The twin Voyagers measured magnetic fields as they traveled out to the far reaches of the solar system, and discovered Uranus and Neptune's magnetospheres.
Other planetary missions including Galileo, Cassini and Juno, and a number of spacecraft that orbit Earth, provide observations to create a comprehensive understanding of how planets form magnetospheres, as well as how they continue to interact with the dynamic space environment around them.
Earth's and other magnetospheres deflect charged particles away from the planet - but also trap energetic particles in radiation belts. Auroras are caused by particles that rain down into the atmosphere, usually not far from the magnetic poles.
It's possible that Earth's magnetosphere was essential for the development of conditions friendly to life, so learning about magnetospheres around other planets and moons is a big step toward determining if life could have evolved there.
One of Jupiter's moons, Io, has powerful volcanic activity that spews particles into Jupiter's magnetosphere. These particles create intense radiation belts and auroras around Jupiter.
Ganymede, Jupiter's largest moon, also has its own magnetic field and magnetosphere - making it the only moon with one. Its weak field, nestled in Jupiter's enormous shell, scarcely ruffles the planet's magnetic field.
On top of that, the magnetic field does not go directly through the center of the planet, so the strength of the magnetic field varies dramatically across the surface. This misalignment also means that Uranus' magnetotail - the part of the magnetosphere that trails behind the planet, away from the Sun - is twisted into a long corkscrew. Neptune
Neptune was also visited by Voyager 2, in 1989. Its magnetosphere is offset from its rotation axis, but only by 47 degrees. Similar to Uranus, Neptune's magnetic field strength varies across the planet. This means that auroras can appear across the planet - not just close to the poles, like on Earth, Jupiter and Saturn. And beyond
Outside of our solar system, auroras, which indicate the presence of a magnetosphere, have been spotted on brown dwarfs - objects that are bigger than planets but smaller than stars. There's also evidence to suggest that some giant exoplanets have magnetospheres, but we have yet to see conclusive proof. As scientists learn more about the magnetospheres of planets in our solar system, it can help us one day identify magnetospheres around more distant planets as well.
Greenbelt MD (SPX) Oct 25, 2017
Like most solar sounding rockets, the second flight of the FOXSI instrument - short for Focusing Optics X-ray Solar Imager - lasted 15 minutes, with just six minutes of data collection. But in that short time, the cutting-edge instrument found the best evidence to date of a phenomenon scientists have been seeking for years: signatures of tiny solar flares that could help explain the mysterious e ... read more
Sun-Earth Missions at NASA
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