Scientists Develop New Models to See How Shocks Associated with CMEs Propagate From the Sun
Scientists have produced new models to see how shocks associated with coronal mass ejections, or CMEs, propagate from the Sun, made possible only by combining data from three NASA satellites to generate a much more robust mapping of a CME than any one could do alone.
CMEs set off interplanetary shocks when they erupt from the Sun at extreme speeds, propelling a wave of high-energy particles, similar to the way ships form bow waves as they glide through water. These particles can spark space weather events around our planet, endangering spacecrafts and astronauts.
By learning more about how a shock develops and accelerates, we will know more about how to predict how it might disrupt near-Earth space. But due to a lack of sensors scattered throughout space, it is impossible to measure directly. Rather, scientists depend on models that use satellite observations of the CME to simulate the ensuing shock’s behavior.
Ryun-Young Kwon, a solar physicist at George Mason University in Fairfax, Virginia, and Johns Hopkins University Applied Physics Laboratory, or APL, in Laurel, Maryland, and APL astrophysicist Angelos Vourlidas, took observations of two different eruptions from three spacecraft: ESA/NASA’s Solar and Heliospheric Observatory, or SOHO, and NASA’s twin Solar Terrestrial Relations Observatory, or STEREO, satellites. One CME erupted in March 2011 and the second, in February 2014.
The scientists fit the CME data to their models — one called the “croissant” model for the shape of nascent shocks, and the other the “ellipsoid” model for the shape of expanding shocks — to reveal the 3-D structure and trajectory of each CME and shock.
Alone, each spacecraft’s observations wasn’t sufficient to model the shocks. But with three sets of eyes on the eruption, each of them spaced almost evenly around the Sun, the scientists could use their models to recreate a 3-D view. Their research confirmed long-standing theoretical predictions of a strong shock near the CME nose and a weaker shock at the sides.
Eventually, shocks travel away from the Sun, and as a result of the 3-D information, the scientists could reconstruct their voyage through space. The modeling helps scientists with important pieces of information for space weather forecasting, in this example, for the first time, they deduced the density of the plasma around the shock and the speed and strength of the energized particles. All of these factors are important for assessing the danger CMEs present to astronauts and spacecrafts. Their results are detailed in a paper published in the Journal of Space Weather and Space Climate published on Feb. 13, 2018.
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