On October 28, 2021, the Sun emitted an X1-class flare and a CME, part of rising activity in Solar Cycle 25. NASA monitors these events to understand their space weather impacts.
Brighter than a shimmering ghost, faster than the flick of a black cat’s tail, the Sun cast a spell in our direction, just in time for Halloween. This imagery captured by NASA’s Solar Dynamics Observatory covers a busy few days of activity between October 25-28 that ended with a significant solar 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 11:35 a.m. EDT.
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, however — when intense enough — they can disturb the atmosphere in the layer where GPS and communications signals travel.
This flare was classified as an X1-class flare. 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.
Second X-Class Flare of Solar Cycle 25
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.
NASA’s fleet of Heliophysics missions keeps constant watch on the Sun and space to help us understand what causes such eruptions on the Sun, as well as how this activity affects space, including near Earth, where it can impact astronauts and satellites.
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