On October 7, 2024, an active sunspot, AR 3842, fired an X2.1 class solar flare, causing temporary radio blackouts in parts of North and South America and over the Pacific Ocean. This event followed another powerful flare from the same sunspot just days earlier. On October 3, AR 3842 emitted the strongest solar flare of Solar Cycle 25, the X9.05 class flare. The last flare, recorded at 3:13 p.m. EDT, caused an increase in ultraviolet radiation, disrupting shortwave radio communications.

Solar flare classifications explained

Solar flares are classified from B-class, which is the weakest, to X-class, which represents the strongest flares. Although the October 7 flare was not as intense as the historic X9.05 of last week, it still produced significant effects, including radio interference. The most powerful solar flare ever recorded occurred in 2003 and was rated as an X45 class event.

Potential Effects of Coronal Mass Ejection (CME)

The US National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Prediction Center confirmed that Monday’s flare involved a coronal mass ejection (CME), which is currently being analyzed for possible impact on Earth. While CME events usually take several days to reach our planet, they can cause geomagnetic storms that disrupt satellites, power grids and GPS signals.

Monitoring solar activity for future risks

Earthward-directed CMEs are of particular concern because they can result in more than just mid-latitude auroras. Stronger solar activity could affect key technological systems. NOAA continues to monitor data from its solar observing satellites, and any potential risks to infrastructure will be assessed based on the strength and direction of the CME.

By monitoring such solar events, scientists strive to better predict and mitigate any adverse effects on Earth’s systems.