February 21, 2014
Sun’s Coronal Mass Ejections Behave Like Crab Nebula’s Gas Tendrils
[ Watch the Video: Enormous Coronal Mass Ejection ]
Lee Rannals for redOrbit.com - Your Universe OnlineResearchers from University College London have explained for the first time the details of how the Sun’s coronal mass ejections (CMEs) behave when falling back onto the star’s surface.
The team has discovered that coronal mass ejections are a lot like the tendrils of gas in the Crab Nebula, which are about 6,500 light-years away from Earth and are millions of times larger.
Scientists witnessed the biggest ejection of material ever seen on June 7, 2011, watching as plasma jumped out of the Sun and made its way out into space. Most of the material from this ejection fell back to the Sun’s surface quickly. Physicists watching this scene unfold saw it as a unique opportunity to study how solar plasma behaves.
“We’ve known for a long time that the Sun has a magnetic field, like the Earth does. But in places it’s far too weak for us to measure, unless we have something falling through it. The blobs of plasma that rained down from this beautiful explosion were the gift we’d been waiting for,” study coauthor David Williams said in a statement.
NASA’s Solar Dynamics Observatory (SDO) has kept an eye on the Sun since 2010, looking through the brightness and providing details about wavelengths of light that are blocked by the Earth’s atmosphere. This NASA instrument helped scientists observe the 2011 eruption in greater detail than ever before.
“We noticed that the shape of the plume of plasma was quite particular,” Jack Carlyle, lead author of the study, said in a statement. “As it fell into the Sun, it repeatedly split apart like drops of ink falling through water, with fingers of material branching out. It didn’t stick together. It’s a great example of an effect where light and heavy fluids mix.”
The team noticed that the falling plasma underwent a phenomenon known as the Rayleigh-Taylor instability as it returned back to the Sun’s surface. This phenomenon causes complex patterns to form by the denser fluid as it splits and branches into “fingers” of matter. A similar effect has been observed before in the Crab Nebula, which is the remnant of a supernova that exploded in the 10th century.
A 1996 study of the Crab Nebula found that the Rayleigh-Taylor instability in the supernova remnant was slightly modified. The magnetized environment around the nebula changes the proportions of the fingers, making them fatter than they would be otherwise.
The researchers of the current study, which has been published in the Astrophysical Journal, witnessed the same effect taking place during the 2011 eruption, even in an area where the Sun’s magnetic field was weak.
Image Below (Left): The plasma falling into the Sun split apart into 'fingers', like ink dops falling through water. Credit: NASA/SDO (Right): Hubble Space Telescope images of the Crab Nebula show similar branching finger-like structures. Credit: NASA, ESA, Alison Loll & Jeff Hester