Our Sun routinely releases radio bursts that can last from a few hours to days. In August 2025, it did something extraordinary, releasing a Type IV radio burst that lasted for 19 days. Type IV radio bursts are produced when electrons trapped inside the Sun’s magnetic fields swirl around and release energy as they go. They are not dangerous, but the magnetic environments that produce them can trigger particle storms into the solar system that can damage satellites and spacecraft. The August event last year was captured by four human probes – NASA’s STEREO, Parker Solar Probe, and Wind missions, alongside ESA and NASA’s Solar Orbiter. None of them got the full picture, and when data from each of them was pieced together, something amazing was revealed.
This radio had lasted for 19 days, nearly four times longer than anything previously recorded. Each of these spacecraft recorded the burst for a few days before it moved onto the next one. The Sun’s rotation led to the source region moving in and out of each of these probes. Scientists applied a new analysis technique to STEREO data, which revealed that the burst was coming from a large magnetic structure in the Sun’s outer atmosphere called a helmet streamer – a distinctive V-shaped feature visible during solar eclipses. In this zone, magnetic field lines arch up from the Sun’s surface and spread into space. The magnetic activity is concentrated in these regions stretching outwards.
Collating data from STEREO, Parker, Wind missions and Solar Orbiter revealed what had happened. Three coronal mass ejections had been released in quick succession from this particular zone, effectively supercharging it. This led to the magnetic trap being constantly fed with material, and this is what kept the radio burst energised far beyond its normal lifespan. The findings were published in the journal Astrophysical Journal Letters. Scientists say that such information is crucial in improving space weather forecasting and better identifying the radio bursts.