NASA: Sun’s corona much larger than previously thought

NASA’s Solar Probe Plus mission will go closer to the Sun than any synthetic technology ever has before.

According to a statement from NASA, scientists using NASA’s Solar Terrestrial Relations Observatory (STEREO) discovered that the huge atmosphere of solar particles surrounding the Sun – called the corona – is much larger than previously believed, extending out for some five million miles above the sun’s surface.  This new information has important implications for NASA’s upcoming Solar Probe Plus mission, which is set to launch in 2018 and go closer to the Sun than any synthetic technology ever has before.
STEREO observations offer the first direct measurements of the inner boundary of the heliosphere, which is the giant bubble sparsely filled with solar particles that surrounds the Sun and all the planets in our Solar System.  By combining measurements from Voyager 1 of the outer boundary of the heliosphere, NASA scientists have now defined the extent of this entire local bubble.
“We’ve tracked sound-like waves through the outer corona and used these to map the atmosphere,” said Craig DeForest of the Southwest Research Institute in Boulder, Colorado.  “We can’t hear the sounds directly through the vacuum of space, but with careful analysis we can see them rippling through the corona.”
The results appeared in The Astrophysical Journal on May 12, 2014.  The researchers observed waves known as magnetosonic waves, a hybrid of sound waves and magnetic waves called Alfven waves. Nothing like sound waves on Earth, which oscillate several hundred times per second, these waves oscillate about once every four hours and are approximately 10 times the length of Earth.
Now that scientists realize the corona extends much further than previously thought, there are important consequences to consider for NASA’s Solar Probe Plus, as the mission will travel to within four million miles of the Sun.
According to NASA’s Solar Probe Plus mission page, the spacecraft will repeatedly sample the near-Sun environment, revolutionizing our knowledge and understanding of coronal heating and of the origin and evolution of the solar wind and answering critical questions in heliophysics that have been ranked as top priorities for decades.