NASA researchers have captured the longest solar radio emission ever observed, exceeding the previous record by almost four times, in a surprising discovery made possible by a groundbreaking new technique.
The event occurred in August 2025 and at first appeared to be nothing out of the ordinary. However, things took a strange turn when the signal surpassed the previous five-day solar radio emission duration record, continuing for 19 days.
Most solar radio emissions cease after just a few hours, although a good number may continue for several days, making the long duration of this event highly unusual. The findings were revealed in a recent paper in the journal Metrologia, which also showcases the new method researchers used, and its applications for exploiting a single data stream to uncover information that usually requires triangulation.
NASA Captures A Strange Emission
Solar radio emissions were first discovered accidentally during World War II after they interfered with British radar systems. Because the phenomenon was considered sensitive to the war effort, it did not appear in scientific literature until 1946, although an independent observation published in 1944 described the signals as “cosmic static.” Since then, astronomers have closely monitored solar radio emissions.
The seemingly innocuous emission first appeared on August 21, 2025, and continued until September 9, 2025. NASA researchers identified the event as a Type IV emission, generated by electrons trapped within solar magnetic fields. These emissions are generally benign and do not produce the kinds of interference that can threaten near-Earth satellites or ground-based electrical infrastructure during more severe solar storms.
Analyzing a Solar Radio Emission
Data for the team’s analysis came from several NASA platforms, including the Solar Terrestrial Relations Observatory (STEREO), the Parker Solar Probe, the Wind mission, and the Solar Orbiter, a European Space Agency collaboration.
No single instrument captured the entire event; instead, each spacecraft observed portions of the unusually long-lasting emission from different vantage points throughout the inner solar system.
Solar Orbiter was the first spacecraft to detect the activity, followed 12 days later by Wind and the Parker Solar Probe, and finally by STEREO one day afterward. Because the event persisted for so long, it passed through several optimal viewing geometries, providing researchers with an unusually rich dataset.
One advancement stemming from the research was the development of a new technique by the NASA team for identifying the source of a radio emission using STEREO data, called the wavevector-corrected ray sphere (WCRS). By applying a correction to direction-finding angles and combining the data with a coronal density model, WCRS allows researchers to perform advanced analysis from only a single data source.
NASA Continues to Probe Solar Activity
WCRS allowed the researchers to key in on a helmet streamer, a type of large magnetic feature residing in the solar atmosphere. The NASA team currently theorizes that coronal mass ejections, a volatile type of solar event known to send harmful waves of space weather toward Earth, likely fueled this intriguing yet significantly less dangerous event.
Three successive coronal mass ejections likely supplied the electrons needed to power the stream.
Researchers believe the new technique could help improve space weather forecasting, an increasingly important concern as modern society becomes more dependent on satellites and communications infrastructure. The method may also enhance scientists’ ability to identify and analyze future radio emissions from the Sun.
The paper, “Unprecedented 19 Day Type IV Radio Emission as a Corotating Electron Reservoir,” appeared in The Astrophysical Journal Letters on May 14, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.