March 19, 2014
Researchers Identify Cause Of Rare, Powerful 2012 Solar Storm
[ Watch the Video: STEREO Captures Fastest CME to Date ]
redOrbit Staff & Wire Reports - Your Universe OnlineResearchers have uncovered the origin and cause of an extreme space weather event that took place July 22, 2012 on the sun which generated the fastest solar wind speed ever recorded directly by a solar wind instrument.
The formation of the powerful event showed remarkable features as a massive cloud of solar material erupted off the sun's right side, zooming out into space and passing one of NASA's twin Solar Terrestrial Relations Observatory, or STEREO, spacecraft along the way.
According to NASA, scientists clocked the speed of this giant cloud, known as a coronal mass ejection, or CME, at more 1,800 miles per second as it left the sun – a speed that would circle the Earth five times in one minute.
CMEs are clouds of magnetic fields and plasma – a hot gas composed of charged particles.
The July 2012 storm was so powerful that had it been aimed at Earth instead of at the STEREO A spacecraft, which was located 120 degrees off to the side of Earth, the consequences could have included satellite malfunctions and potential failures within ground-based electricity grids.
The researchers suggest that the successive, one-two punch of solar CMEs is what caused the storm to be so powerful. Such in-transit interaction between two closely launched CMEs resulted in an unusually violent and fast-moving space weather event, the scientists said.
"In a sense, this was the 'perfect storm'," said research assistant professor Noé Lugaz of the University of New Hampshire’s Institute for the Study of Earth, Oceans, and Space (EOS).
"The first, fast eruption greased the skids for the quick propagation of the subsequent, extremely fast eruptions through interplanetary space,” said Lugaz, who co-authored a paper about the findings published Tuesday in the journal Nature Communications.
"These results provide a new view crucial to solar physics and space weather as to how an extreme space weather event can arise from a combination of multiple solar eruptions.”
Charles Farrugia, an EOS research professor and coauthor of the paper, compared the 2012 storm to another powerful storm that occurred more than 150 years ago.
"Remarkably, this is reminiscent of the great solar flare in 1859, the Carrington Event, and the geomagnetic storm of unheard of intensity in Earth's magnetosphere, or magnetic field, that occurred less than one day later,” he said.
Although scientists are not yet clear on how such extreme space weather storms form and evolve, building a better understanding of their causes is one of the key goals of the STEREO mission. Indeed, detecting the successive eruptions of the July 2012 storm would not have been possible prior to STEREO.
"STEREO has dramatically improved our understanding of the powerful solar eruptions that can send more than a billion tons of the sun's outer atmosphere hurtling into space,” said Antoinette Galvin, EOS research professor and principal investigator on STEREO's PLAsma and Supra-Thermal Ion Composition (PLASTIC) instrument, which detected the extremely fast solar wind protons.
PLASTIC, together with the University of California, Berkeley-led In-situ Measurements of Particles and CME Transients (IMPACT) instrument, made the critical measurements of the July 2012 solar storm.
The STEREO mission, which launched in October 2006, is comprised of two nearly identical spacecraft the size of golf carts. Their observations enable scientists to construct the first-ever three-dimensional views of the sun. PLASTIC provides plasma characteristics of protons, alpha particles and heavy ions. Solar wind protons and alpha particles constitute most of the mass in the solar wind and are therefore the primary components exerting kinetic pressure on the Earth's magnetosphere—one of the drivers for space weather.