SURPRISE GEOMAGNETIC STORM: A minor yet effective interplanetary shock wave hit Earth's magnetic field on May 4th (1450 UTC), sparking G2-class (Moderate) geomagnetic storms and auroras. The source of the shock wave is uncertain, probably a stealthy CME that left the sun late last week. Minor G1-class storms are likely on May 5th as we transit the CME's magnetized wake. Free: Space Weather Newsletter
ARE WE OVERDUE FOR A SUPERFLARE? We've all heard of X-class solar flares--powerful explosions on the sun that pepper satellites with energetic particles and trigger great geomagnetic storms. They can be scary. But not as scary as a new category of solar flare being discussed by researchers: the "S-flare"--a solar superflare stronger than X10.
A new paper published in the Journal of Geophysical Research suggests we may be overdue for one.
During the current solar cycle (Solar Cycle 25), Earth has not yet experienced an S-flare. That's a little unusual, according to researchers led by V.M. Velasco Herrera of the National Autonomous University of Mexico. The team looked at 50 years of data from Earth-orbiting satellites. Among 95,627 solar flares, they found 37 Earth-directed S-flares. Every solar cycle since the 1970s has produced one--except Solar Cycle 25.
There are some clues to when the next S-flare might happen. In the 50-year dataset, the researchers found two underlying rhythms: 1.7 years and 7 years, both linked to magneto-Rossby waves inside the sun. When both rhythms swing into their positive phase at the same time, the probability of an S-flare spikes.
Right: An S-class solar flare (X45) on Nov. 4, 2003. [more]
According to those rhythms, we're exiting a high-risk S-flare window now: mid-2025 through mid-2026. The next high-risk window opens in early 2027 and lasts about 6 months.
In May 2024, Europe's Solar Orbiter detected two possible S-flares on the farside of the sun. Their intensity (with significant error bars) was X11.1 and X16.5. The sun fired the gun; we just happened to be standing behind the target.
Maybe next time. Stay tuned for updates as the 2027 window approaches.
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MOTHER'S DAY IS THIS SUNDAY: Are you looking for an out-of-this world Mother's Day gift? Consider this: Every time the students of Earth to Sky Calculus launch a cosmic ray balloon, they include something extra in the payload--something Mom will love:
Every item in the Earth to Sky Store has flown to the edge of space and comes with a greeting card showing the item in flight. The interior of the card tells the story of the gift's journey from launch to landing. Mom-satisfaction guaranteed!
Far Out Gifts: Earth to Sky Store
All sales support hands-on STEM education
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