Lead: On May 10, the Sun produced a powerful M5.7-class solar flare accompanied by a coronal mass ejection (CME), sending a burst of particles and radiation into space. The flare caused a brief radio blackout over the Atlantic Ocean at the time of the eruption, according to NOAA’s Space Weather Prediction Center. Instruments on SOHO captured the CME in coronagraph imagery, showing the eruption and a bright speck identified as Mercury nearby. Forecasters say a glancing impact from the CME could spark minor geomagnetic activity and increased aurora chances later this week.
Key Takeaways
- The eruption on May 10 reached M5.7 strength, a powerful M-class flare level capable of disrupting HF radio communications.
- NOAA reported a radio blackout affecting the sunlit side of Earth over the Atlantic during the flare, consistent with intense X-ray and UV emission.
- SOHO LASCO imagery shows the CME expanding from the Sun; a bright speck near the cloud was identified as Mercury in the frames.
- While not expected to match the May 10, 2024 G5 geomagnetic storm, forecasters warn a weak, glancing blow could produce minor geomagnetic storm conditions later this week.
- NOAA’s Space Weather Prediction Center and the U.K. Met Office both say sunspot regions AR4436 and AR4432 remain active and could produce more M-class—and possibly X-class—flares in the coming days.
- A repeat of the 2024 G5-level impacts is not predicted; forecasters emphasize uncertainty in CME trajectory and arrival strength.
Background
Solar flares are categorized on an A–X scale, with each letter step representing a tenfold increase in peak X-ray flux; M-class flares are the second-highest common category and can affect high-frequency radio and navigation signals. Coronal mass ejections are large expulsions of magnetized plasma that may drive geomagnetic storms if their path intersects Earth. The Sun follows an approximately 11-year activity cycle; we are currently in a phase of heightened sunspot development that raises the probability of frequent M- and X-class eruptions.
On May 10, 2024, Earth received effects from an extreme G5 geomagnetic storm—the first classified G5 since 2003—producing auroras seen deep into mid-latitudes. That historical benchmark remains a touchstone for forecasters and aurora chasers when assessing the significance of new eruptions on the same calendar date. The active regions now producing flares, labeled AR4436 and AR4432, are closely watched by operational space weather centers because their magnetic complexity favors large eruptions.
Main Event
The sequence began with an M5.7-class flare that registered in solar X-ray monitors on May 10. Instruments recorded an abrupt spike in X-ray and extreme ultraviolet output, which caused ionization changes in the sunlit portion of Earth’s upper atmosphere and led to documented HF radio blackouts over the Atlantic. NOAA’s Space Weather Prediction Center flagged the event and issued routine alerts to aviation and maritime stakeholders.
Coronagraph images from the SOHO LASCO C2 and C3 instruments captured the CME as it expanded away from the Sun; the C3 frame shows the cloud erupting from the upper-left sector while a bright point to the right was identified as Mercury. Analysts examined the CME’s direction and speed to estimate whether Earth would receive a central hit or a glancing encounter—forecasts lean toward a grazing impact rather than a direct strike.
Operational models project that the CME, if it clips Earth, will likely produce only minor geomagnetic storm levels (G1–G2), but uncertainty in cloud structure and interplanetary magnetic field orientation could modulate that outcome. Both NOAA and the U.K. Met Office released bulletins noting active sunspot regions and a non-zero probability of additional M-class flares and isolated X-class events in the next several days. Ground-level impacts are expected to be limited, though aviation HF users and radio amateurs were advised to monitor alerts.
Analysis & Implications
Technically, the primary near-term effect of a strong flare like M5.7 is enhanced ionization of the dayside ionosphere, producing short-lived HF radio blackouts and possible GNSS (GPS) signal degradation in affected sectors. The May 10 radio blackout over the Atlantic demonstrates this mechanism: intense X-rays and EUV flux temporarily altered ionospheric propagation for hours. Critical services that rely on HF and some satellite links maintain contingency procedures, but repeated strong flares can elevate operational risk for certain routes and activities.
Geomagnetic impacts from the accompanying CME depend heavily on the CME’s magnetic field orientation upon arrival. If the CME’s interplanetary field turns southward, coupling with Earth’s magnetosphere can drive stronger geomagnetic activity and spark visible auroras at lower latitudes. Current trajectory assessments favor a glancing blow, which would likely produce only localized or marginal auroral displays rather than the deep mid-latitude shows of the May 10, 2024 G5 event.
From an economic and infrastructure perspective, most modern systems can tolerate occasional M-class flares with minimal disruption, but cascading risks exist for poorly protected grid components, high-latitude pipelines and long-range HF-dependent operations. Continued active flare production from AR4436 and AR4432 raises the short-term probability of further alerts; agencies will be watching solar wind parameters, CME speed, and magnetic orientation to update impact forecasts.
Comparison & Data
| Metric | Typical Range / Value | Example |
|---|---|---|
| Solar flare classes | A → B → C → M → X (each step ×10 in X-ray flux) | M5.7 (May 10 event) |
| Geomagnetic G-scale | G1 (minor, Kp=5) → G5 (extreme, Kp=9) | G5 storm (May 10, 2024) |
| Reported radio blackout | Localized HF outages on sunlit hemisphere | Atlantic region (May 10, M5.7 flare) |
The table places the May 10 M5.7 flare in context: it is a strong M-class event but below X-class. The May 10, 2024 G5 geomagnetic storm—driven by a different, more geoeffective CME—is the relevant comparison for worst-case aurora and infrastructure impacts. Operational centers combine these classification systems with in-situ solar wind data to produce arrival-time and impact confidence estimates.
Reactions & Quotes
Operational centers issued measured statements about immediate impacts and outlooks for additional activity. NOAA emphasized the observed radio blackout and ongoing monitoring of active regions.
We recorded an M5.7 flare that caused short-lived HF radio blackouts; our models show a potential glancing CME arrival later this week.
NOAA Space Weather Prediction Center (official)
Public-facing scientists noted the difference between this eruption and the extreme 2024 event, advising aurora watchers to temper expectations while remaining prepared for possible displays.
While this CME is unlikely to recreate the May 10, 2024 G5 storm, a weak impact could still produce visible auroras at higher latitudes.
U.K. Met Office (official)
A community of amateur aurora hunters and radio operators reported brief HF disruptions and shared SOHO frames; their field reports help corroborate model-driven alerts.
We saw brief HF fading over the Atlantic and clear coronagraph imagery showing the CME heading outward.
Aurora/radio monitoring community (observers)
Unconfirmed
- Whether the CME’s magnetic field will turn strongly southward on encounter—this orientation determines whether geomagnetic effects will intensify and is not yet measured.
- Claims of specific mid-latitude cities seeing bright auroras from this event are not confirmed and depend on the CME’s eventual strength and Earth’s magnetic response.
- Any cascading impacts to national power grids or satellites from this specific CME remain speculative until in-situ solar wind and magnetometer data confirm a stronger arrival.
Bottom Line
The May 10 M5.7 flare and associated CME are significant solar events that produced measurable effects—most notably a transient HF radio blackout over the Atlantic—and yielded clear coronagraph imagery from SOHO. Forecasters currently assess the CME as likely to produce only a glancing interaction with Earth, making strong, widespread auroras unlikely but leaving room for localized enhancements at higher latitudes.
Agencies including NOAA and the U.K. Met Office will continue to monitor AR4436 and AR4432 for further M- or X-class activity; operators and hobbyists who rely on HF communications or hope to see auroras should follow official updates and watch the modeled CME arrival windows and solar wind measurements. The situation illustrates both the routine hazards of an active Sun and the importance of timely observational networks for predicting space weather impacts.
Sources
- Space.com (news)
- NOAA Space Weather Prediction Center (official agency)
- U.K. Met Office Space Weather (official agency)
- SOHO / LASCO imagery (observatory/mission)