Thursday, March 20, 2014

NASA STEREO: UNH detector illuminate cause of sun's 'perfect storm'

This image combines data from two coronagraphs and an extreme ultra-violet imager (green) on STEREO A. 

The CME is the bright streaks emanating from the sun. 

A coronagraph is a telescope that uses a disk to block the sun's bright surface revealing the solar corona. 

Credit: NASA.

An international team of scientists, including three from the University of New Hampshire's (UNH) Space Science Center, uncovers the origin and cause of an extreme space weather event that occurred on July 22, 2012 at the sun and generated the fastest solar wind speed ever recorded directly by a solar wind instrument.

The formation of the rare, powerful storm showed striking, novel features that were detected by a UNH-built instrument on board NASA's twin-satellite Solar TErrestrial RElations Observatory (STEREO) mission.

An instrument led by the University of California, Berkeley also made key measurements.

The 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 would have been dramatic: widespread aurora, satellite malfunctions, and potential for failures with ground-based electricity grids.

To date, it has been unclear how extreme space weather storms form and evolve.

Developing a better understanding of their causes is vital to protect modern society and its technological infrastructures, and is one of the goals of the STEREO mission.

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"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," says research assistant professor Noe Lugaz of the UNH Institute for the Study of Earth, Oceans, and Space (EOS) and a coauthor on the Nature Communications paper.

Lead author is Ying D. Liu of the State Key Laboratory of Space Weather, National Space Science Center and Chinese Academy of Sciences.

The authors suggest it was the successive, one-two punch of solar eruptions known as coronal mass ejections (CMEs) that was the key to the event, which blasted away from the sun at 3,000 kilometers per second-a speed that would circle the Earth five times in one minute.

Detecting the successive eruptions would not have been possible prior to STEREO.

"In a sense, this was the 'perfect storm'," Lugaz says. "The first, fast eruption greased the skids for the quick propagation of the subsequent, extremely fast eruptions through interplanetary space."

More Information: Nature Communications Journal - 'Observations of an extreme storm in interplanetary space caused by successive coronal mass ejections' Ying D. Liu, Noé Lugaz, et al. doi:10.1038/ncomms4481

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