A powerful X1.6-class solar flare (Sept. 10 @ 17:46 UT)
X-FLARE: Earth-orbiting satellites have just detected a powerful X1.6-class solar flare (Sept. 10 @ 17:46 UT). The source was active sunspot AR2158, which is directly facing Earth. NASA’s Solar Dynamics Observatory recorded the extreme ultraviolet flash:
Ionizing radiation from the flare could cause HF radio blackouts and other communications disturbances, especially on the day-lit side of Earth. In the next few hours, when coronagraph data from SOHO and STEREO become available, we will see if a CME emerges from the blast site. If so, the cloud would likely be aimed directly at Earth and could reach our planet in 2 to 3 days. Stay tuned for updates about geomagnetic storms in the offing. Aurora alerts: text, voice
UPDATED STORM FORECAST: NOAA forecasters have issued a geomagnetic storm warning for Sept. 12th when a CME launched on Sept. 9th (see below) is expected to deliver a glancing but potent blow to Earth’s magnetic field. The storm could reach moderate intensity (G2-class) with auroras visible across northern-tier US states such as Maine, Michigan, and Minnnesota. Another CME could be following close on its heels if today’s X-flare also launched a cloud in our direction. It all adds up to a high probability of geomagnetic storms in the days ahead. Aurora alerts: text, voice
LONG DURATION FLARE AND EARTH-DIRECTED CME: Yesterday, the magnetic canopy of sunspot AR2158 erupted, producing an explosion that lasted more than 6 hours. The flare peaked on Sept. 9th at 00:30 UT with a classification of M4 on the Richter Scale of Solar Flares. Long-duration flares tend to produce bright CMEs, and this one was no exception. Coronagraphs onboard the Solar and Heliospheric Observatory observed a CME racing out of the blast site at nearly 1,000 km/s (2.2 million mph):
Most of the storm cloud is heading north of the sun-Earth line, but not all. A fraction of the CME will deliver a glancing blow to Earth’s magnetic field during the early hours of Sept. 12th. In the past few weeks, glancing blows from minor CMEs have sparked beautiful auroras around the Arctic Circle. This CME could spark even better displays. NOAA forecasters estimate a 79% (not a typo: 79%) chance of polar geomagnetic storming on Sept. 12th. Aurora alerts: text, voice
ISS-SUNSPOT CONJUNCTION: Yesterday a dark winged form flew across the face of the sun. It was the International Space Staton (ISS) having a close encounter with active sunspot AR2158:
Enrico Finotto recorded the transit from Venice, Italy. “I took the picture using a Canon 600D set at ISO 400 and a solar-filtered Vixen 102FL refractor,” he says.
Orbiting Earth at 17,000 mph, the space station crossed the face of the sun in just a fraction of a second. Finotto knew precisely when to take the picture thanks to a prediction from Calsky.com. “They are always accurate,” says Finotto.
The sunspot pictured alongside the ISS in Finotto’s photo, AR2158, has a “beta-gamma-delta” magnetic field that harbors energy for strong eruptions. NOAA forecasters estimate a 75% chance of M-class flares and a 30% chance of X-flares on Sept. 10th.
Related: The classification of solar flares