On September 10, 2014, NASA’s IRIS satellite observed an X1.6 class flare based on the high intensity of X-ray radiation. “X-class” events are the most powerful, and this one comes on the heels of another large flare two days earlier. The region responsible for these bursts, Active Region 12158, was situated just right of Sun-center in a perfect location for plasma ejected by the flares to collide with Earth. It’s very difficult to accurately predict what the impact at Earth will be, but we’re likely to experience some geomagnetic storm activity as these eruptions wash over the planet in 2-3 days, possibly triggering auroras at high latitudes.
IRIS observations at 17:28 UT, a few minutes before the flare peak are shown at right. The right side of the image is an ultraviolet observation of the Sun’s so-called “interface region,” which separates the thousand-degree surface from the million-degree corona (outer atmosphere). A bright ribbon snakes through the image, representing footpoints of the hot plasma loops in the corona that produced the flare-defining X-rays. IRIS’ mission is to understand what happens in the interface region to make the plasma above it so hot. It does this by splitting the light along the black line down the center of the image into its many wavelengths, a technique called spectroscopy. The left side of the IRIS image shows light produced by magnesium atoms at a very specific energy level. By examining which atoms light up and when, scientists hope to learn more about the physical processes that heat the corona and the related processes that underly solar eruptions. The CME associated with a September 10, 2014, X1.6 flare is visible in this image from the joint European Space Agency and NASA’s Solar and Heliospheric Observatory. Credit: ESA&NASA/SOHO The IRIS team is led by the Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), who built the spacecraft and instrument detector. The telescope was built by the Smithsonian Astrophysical Observatory (SAO), which also assists in operations and data analysis.
