This imagery captured by NASA’s Solar Dynamics Observatory (SDO; link) covers a busy period of activity in October, during which we witnessed an X1.0-class X-ray flare.
From late afternoon October 25 through mid-morning October 26, an active region on the left limb of the Sun flickered with a series of small flares and petal-like eruptions of solar material.
Meanwhile, the Sun was sporting more active regions at its lower center, directly facing Earth. On October 28, the biggest of these released a significant flare, which peaked at 15:35, 28 Oct 2021 UTC.
This X1.0 X-ray flare that erupted from Active Region 12887 (we typically drop the left-most digit when referring to an active region, so this is AR2887) is the second X-class flare of Solar Cycle 25, as of the time this video goes live.
The first X-class flare occurred on 3 July 2021 and measured X1.59. It, too, caused an HF radio blackout. These blackouts will occur more often as the cycle activity increases, because the higher sunspot activity leads to many more flares, and thus cause the geomagnetic storms as the typical CME is erupted out into space, possibly colliding with Earth’s magnetosphere.
Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth’s atmosphere to physically affect humans on the ground. When intense enough, they can disturb the atmosphere in the layer where GPS and communications signals travel. Some of these disturbances to communications are called radio blackouts. They cause the lower layers of the ionosphere to become more ionized, which results in the absorption of shortwave radio frequency signals.
This flare on October 28 was classified as X1.0 in intensity. X-class denotes the most intense flares, while the number provides more information about its strength. An X2 is twice as intense as an X1, an X3 is three times as intense, and so on. Flares that are classified X10 or stronger are considered unusually intense.
This was the second X-class flare of Solar Cycle 25, which began in December 2019. A new solar cycle comes roughly every 11 years. Over the course of each cycle, the Sun transitions from relatively calm to active and stormy, and then quiet again; at its peak, known as solar maximum, the Sun’s magnetic poles flip.
Two other eruptions blew off the Sun from this active region: an eruption of solar material called a coronal mass ejection and an invisible swarm of solar energetic particles. These are high-energy charged particles accelerated by solar eruptions.
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