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Dernière mise à jour : le 18/05/2022 à 12:37

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Just when scientists were thinking the solar maximum was over, the sun has hurtled another flare at Earth from the largest and most complex group of sunspots seen in a decade. The bubble of magnetized hot gases the flare released is expected to hit Earth on Saturday morning and create stormy space weather for the weekend. A strong geomagnetic storm could light up early morning skies with aurorae at high latitudes and cause electrical trouble for communication satellites. But the massive sunspot group dubbed "Region 9393" isn't finished yet.

Instead of shrinking after releasing a flare and a bubble of superheated gases on Thursday morning, it's still getting bigger, say space weather forecasters at the National Oceanic and Atmospheric Administration's Space Environment Center in Boulder, Colo. "It's still very large and still growing in size," says forecaster Bill Murtagh.

Already the area of Region 9393 exceeds that of 13 Earths. In checking their records, solar scientists have had to look back to 1991 — the last solar maximum — to find anything of similar size, he says. It's definitely the biggest, most complex sunspot group to be seen in a decade.

By complex, Murtagh is referring to it being full of different magnetic fields that are arcing off each other, like batteries jumbled together and allowed to connect and reconnect in chaotic ways. Such complex regions are known to produce the most powerful flares and ejections of hot gases, he says.

Region 9393 has also rotated onto the western limb of the sun, a position that puts it in better — and more dangerous — electrical connection with the Earth. Any more big flares from the region before it rotates out of view could deal powerful blows to orbiting spacecraft and electrical systems on Earth.

Space weather forecasters are predicting geomagnetic storms to hit G-3 to G-4 levels over the weekend (on a scale where G-5 is maximum). The upsurge in solar activity comes just about a year after the sun reached the peak of its 11-year sunspot cycle, said solar scientist Jo Ann Joselyn of the University of Colorado in Boulder.

The surge of sunspots isn't entirely unusual, but it follows an unusually quiet sun in February that resembled the spotless, quiet sun of the low end of the sun's cycle. That quiet period had led some to think the solar maximum was all over.

Source :NASA

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