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During early September, the sun produced an abnormally strong active region (AR 12673). AR 12673 produced 3 X-flares, including the brightest flare of solar cycle 24 (a X9.3 flare). The brightest flare's X-ray luminosity caused radio blackouts within 10 minutes across the Atlantic. In addition to increasing the X-ray luminosity, the brightest flare produced a Coronal Mass Ejection (CME for short). The CME contained gas from the solar corona. The gas arrived at earth approximately 36 hours after the flare and created a severe geomagnetic storm.
The above XRT movie shows two of the X-flares from AR 12673, including the X9.3 flare, with an image of earth for scale. The first flare saturates the detector creating columns of bright pixels, which do not contain physically relevant information. Once the saturation ends, a bright (hot) gas blob moves from the brightest region to the top right portion of the active region. The hot gas's introduction coincides with the active region's uncoiling. About an hour after the active region finishes uncoiling, the second/brightest flare occurs and saturates the detector. While the brightest regions saturate, relatively faint hot gas expands away from the active region. The hot gas accelerates with enough energy to escape the sun's gravity, creating a CME.Tweet
Keywords: Flare, CME, Sigmoid