On June 19, 2025, a powerful X1.9-class solar flare erupted from sunspot region AR4114, peaking at 9:50 p.m. EDT (0150 GMT June 20), causing shortwave radio blackouts across the Pacific Ocean, including Hawaii. The flare released intense X-rays and ultraviolet radiation, ionizing Earth's upper atmosphere and disrupting high-frequency radio signals below 25 MHz. Ham radio operators and aviators likely experienced signal loss. No coronal mass ejection (CME) was associated with this flare, so no auroras are expected. The sunspot remains active, with a 30% chance of further X-class flares through June 22, potentially causing more disruptions.
Here's a breakdown of the event and its impact:
- What happened? Sunspot region 4114, which has been highly active, unleashed an X1.9-class solar flare. X-class flares are the most powerful type of solar flare, and an X1.9 is considered a strong eruption within this category.
- When did it peak? The flare peaked at 9:50 p.m. EDT on June 19 (0150 a.m. GMT June 20).
- Impact on radio signals: The intense burst of electromagnetic radiation from the flare, particularly X-rays and extreme ultraviolet radiation, traveled at the speed of light and reached Earth almost instantly. This radiation ionized Earth's upper atmosphere (specifically the D-layer of the ionosphere) to a much higher degree than usual.
- Why did it cause blackouts? Normally, high-frequency (HF) radio waves rely on the ionosphere to bounce signals over long distances. However, the increased ionization in the lower, denser layers of the ionosphere caused the radio waves to lose energy from frequent collisions with electrons, leading to the degradation or complete absorption of signals. This resulted in a "radio blackout" primarily affecting frequencies below 25 MHz (or 30 MHz in some reports).
- Affected regions: The shortwave radio blackouts were centered over the Pacific Ocean, with Hawaii being particularly impacted. Ham radio operators and aviators in these areas likely experienced a sudden loss of signal.
- No CME (Coronal Mass Ejection): While this was a powerful flare, it was not accompanied by a coronal mass ejection (CME). CMEs are large expulsions of solar plasma and magnetic fields that, if Earth-directed, can cause geomagnetic storms and auroras. The absence of a CME means there are no immediate concerns for widespread power grid disruptions or spectacular aurora displays from this specific event.
- Ongoing monitoring: Sunspot region 4114 remains Earth-facing and magnetically complex, indicating it could produce more high-level flares in the coming hours or days. Space weather forecasters are closely monitoring its activity.
This event serves as a reminder of how solar activity can directly affect Earth's technological infrastructure, particularly communications systems that rely on the ionosphere.