Web edition: October 8, 2012
Print edition: November 17, 2012; Vol.182 #10 (p. 12)
A pair of giant gassy plumes recently ejected by the sun ricocheted off each other like bouncy balls, changing solar physicists’ ideas about how these eruptions of charged particles and magnetic fields can behave.
Captured on camera by NASA’s Solar Terrestrial Relations Observatory probes in November 2008, the two balls of charged gas smashed together and rebounded with more energy of motion than they had initially, scientists report online October 7 in Nature Physics. The phenomenon is known as a superelastic collision.
“Such a phenomenon is not frequently observed in nature,” says study coauthor Yuming Wang, a physicist at the University of Science and Technology of China in Hefei. Scientists have observed it on the scale of small particles, but not with massive balls of charged gas. The finding was “very surprising,” Wang says.
These massive solar eruptions, known as coronal mass ejections, possess an amount of energy on the order of a billion atomic bombs, Wang says. Understanding how the eruptions interact is critical for predicting space weather, conditions that affect communications satellites and spacecraft.
In the case of these solar eruptions, scientists want to know when the fallout will hit Earth, says atmospheric and space scientist Noé Lugaz of the University of New Hampshire. “Collisions are more likely to cause intense events on Earth than individual eruptions. It’s important to pinpoint where they are and reduce damage,” Lugaz says.
The collision observed by Wang and his team boosted the total energy of motion in the ejections by 6.6 percent. But because energy cannot be created or destroyed, that extra energy had to come from somewhere. The researchers suggest that magnetic and heat energy in the charged gas balls was converted to movement energy as they were expanding.
Not all collisions between solar eruptions are superelastic, however, and the November 2008 eruptions are only one case study, Wang says. “We need to analyze more cases and confirm our results.”
Only a handful of these collisions have been studied in detail, and some showed very different behavior. Solar physicist Manuela Temmer at the University of Graz in Austria and colleagues recently reported a collision of two solar eruptions that merged and slowed down dramatically. But Temmer says the new results don’t contradict hers because the collisions occurred under different conditions.
C. Shen et al. Super-elastic collision of large-scale magnetized plasmoids in the heliosphere. Nature Physics. Published online October 7, 2012. doi: 10.1038/NPHYS2440. [Go to]
M. Temmer et al. Characteristics of kinematics of a coronal mass ejection during the 2010 August 1 CME-CME interaction event. Astrophysics J. Vol. 749, February 3, 2012. [Go to]