image: OVRO-LWA radio data contrasts a quiet day (Sept. 29, 2025) with the hours after the X1.7-class flare recorded at 2:35 ET on Nov. 9. The type III radio bursts, shown in the radio dynamic spectrum (horizontal axis is UT time, vertical axis is frequency), appear nearly vertical bursts during stable ionospheric conditions. After flare-driven X-ray and UV radiation ionized the lower ionosphere and geomagnetic storms driven by the associated coronal mass ejections, these radio bursts became curved and chaotic, particularly at low frequencies (bottom of the plot).
Credit: NJIT/OVSA Team
As this month’s string of powerful X-class solar flares sparked brilliant aurorae that lit up skies across an unusually wide swath of the globe — from northern Europe to Florida — researchers at NJIT’s Center for Solar-Terrestrial Research (CSTR) captured a less visible, but crucial, record of the storm’s impact on Earth’s upper atmosphere.
Recent measurements recorded by NJIT’s new network of radio telescopes show how a rare sequence of intense flares from Nov. 9–14, including an X5.1 event marking 2025’s strongest flare so far, jolted the ionosphere — the plasma-filled atmospheric layer essential for radio signals, GPS accuracy and satellite orbits.
The flares triggered R3 (strong) radio blackouts across Africa and Europe, with several coronal mass ejections (CMEs) fueling a major geomagnetic storm and aurora at unusually low latitudes.
The cluster of explosive events originated from a single active region on the Sun, AR4274.
“It’s somewhat unusual to see four X-class flares in just a few days from the same region,” said Bin Chen, NJIT-CSTR professor of physics and director of the Expanded Owens Valley Solar Array (EOVSA). “An X1.7 flare on Nov. 9, an X1.2 on Nov. 10, an X5.1 on Nov. 11 and an X4.0 on Nov. 14 — that’s a very productive stretch. What really stood out were the ripple effects right here on Earth.”
Though the flares occurred during nighttime in California — out of view of NJIT’s Big Bear Solar Observatory — the center’s radio telescopes at the Owens Valley site in the Eastern Sierra recorded the flares’ aftermath and their disturbances in real time.
EOVSA and the newly operational Long Wavelength Array at Owens Valley Radio Observatory (OVRO-LWA) tracked dramatic atmospheric changes across a broad range of radio frequencies — from microwaves observed by EOVSA (similar to those used in satellite communications and Wi-Fi) down to the meter- and decameter waves captured by OVRO-LWA (similar to FM radio frequencies).
“Normally, OVRO-LWA radio data often show neat, nearly vertical bursts known as type III radio bursts,” said Chen. “After these flares, these bursts are curved and chaotic at low frequencies — a clear sign the ionosphere had been disturbed.”
For ionospheric scientists, the event was nearly as striking as the aurora.
“This storm was an excellent reminder that Earth is part of a much larger cosmic system,” said Lindsay Goodwin, NJIT-CSTR assistant professor of physics and ionosphere expert. “Not all extreme solar activity leads to a geomagnetic storm — sometimes the material misses Earth. But in this case, it hit.”
The result was a G4 geomagnetic storm on NOAA’s five-point scale.
“The Dst index, which measures how much Earth’s magnetic field is compressed by the solar wind, plunged from about –40 nT to nearly –250 nT in just a few hours,” Goodwin said. “That’s a huge shock to our planet’s magnetic defenses.”
Charged particles raining into the atmosphere produced auroras, and this event was extreme enough to push aurora far beyond their usual range, with sightings reported as far south as Florida.
“My aurora chat group was exploding with images from places that almost never see northern lights,” Goodwin said.
The episode also demonstrated the growing capability of NJIT’s radio observatories. OVRO-LWA recently entered full solar-science operations, opening a new window into the Sun’s “middle corona” — a region from about 1.5–10 solar radii where magnetic fields restructure and CMEs accelerate.
Supported by a $4.2 million National Science Foundation award, OVRO-LWA and EOVSA now operate together as an integrated community radio facility dedicated to solar and space weather research, referred to as the Owens Valley Solar Arrays (OVSA).
“This dataset is new by itself,” said Chen. “OVRO-LWA complements EOVSA perfectly. Together, they let us follow space-weather effects from their origin in the solar corona all the way to their impact on Earth’s upper atmosphere.”
Goodwin’s team, with help from NJIT undergrad Jeremy McLynch, recently added another dimension to the analysis.
Over the summer, their team deployed a high-precision GPS receiver beside the OVRO-LWA — nicknamed FLUMPH (Field-deployed L-band Unit for Monitoring Phase Hiccups), after the popular Dungeons & Dragons creature it resembles.
The device captures real-world disruptions to satellite-navigation signals during solar storms.
“Plasma irregularities caused by solar and geomagnetic activity disrupt radio and GPS communication,” Goodwin said. “Pairing GPS measurements with the LWA data lets us see both sides of the story — how the Sun shakes the ionosphere, and how that affects the technologies we rely on daily.”
For now, both Chen and Goodwin say the space weather research community is still unpacking the storm’s full impact. With the Sun near the peak of its 11-year activity cycle, Goodwin says similar storms are possible near-term.
“Scientists are only beginning to understand the full effects of this storm,” Goodwin said. “Historically, extreme solar and geomagnetic events can disrupt power grids, interfere with radio communications, and threaten the safety and operation of satellites and spacecraft. We’ve seen several major storms recently, because the Sun is still near the peak of its 11-year cycle.
“Such events will become less common as the Sun quiets down, but they will return in roughly 11 years — and when they do, understanding them will be even more important as we rely more on space technology and venture farther into space.”