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Sigmoid Solar Eruption Sparks Minor Geomagnetic Storm

9/10/2025

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Summary

Story summary

On September 4, 2025, an S-shaped structure appeared on the sun, preceding an M-class solar flare that triggered a coronal mass ejection (CME) towards Earth.
The CME, measuring 435,000 miles, disrupted Earth's magnetic field on September 7, resulting in a minor geomagnetic storm.
This "sigmoid eruption" is associated with twisted magnetic fields around sunspots.
The S-shape suggests a heightened risk of solar flares, similar to the X9.3 flare observed in 2017.
Solar activity is currently elevated during the solar maximum phase, exceeding predictions, prompting ongoing research into sigmoid eruptions.

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Story summary

On September 4, 2025, an S-shaped structure appeared on the sun, preceding an M-class solar flare that triggered a coronal mass ejection (CME) towards Earth.
The CME, measuring 435,000 miles, disrupted Earth's magnetic field on September 7, resulting in a minor geomagnetic storm.
This "sigmoid eruption" is associated with twisted magnetic fields around sunspots.
The S-shape suggests a heightened risk of solar flares, similar to the X9.3 flare observed in 2017.
Solar activity is currently elevated during the solar maximum phase, exceeding predictions, prompting ongoing research into sigmoid eruptions.