“Very strong” solar storm causes radio outage in aurora forecast over the USA

A massive solar flare spewed by the sun caused radio blackouts across South America and the mid-Atlantic on Saturday.

The sunspot responsible for the “very strong” class X4.5 eruption – called sunspot AR3825 – also emitted a large cloud of solar plasma that is moving toward Earth.

When this coronal mass ejection (CME) hits the atmosphere, it is expected to trigger G3-class geomagnetic storms, making the Northern Lights visible as far south as California, Missouri, and Colorado, according to spaceweather.com.

Solar flares and CMEs occur when magnetic energy built up in the Sun's atmosphere is suddenly released, usually near sunspots. Solar flares are powerful bursts of radiation – including X-rays and ultraviolet (UV) light emitted by the Sun – while CMEs are huge chunks of solar plasma and magnetic field.

Radiation from solar flares can cause radio blackouts because it affects the Earth's ionosphere, a layer of the atmosphere filled with charged particles. This layer is important for communications because it reflects high-frequency radio waves, allowing long-distance communication. Increased intensity of X-rays and UV radiation causes a burst of ionization in the ionosphere, causing the ionosphere to absorb high-frequency radio waves instead of reflecting them, causing radio signals to weaken or disappear altogether.

“The Earth's ionosphere is a region of our atmosphere between 80 and 600 km above the Earth's surface. The ionosphere is very sensitive to X-rays from the Sun and during an outburst, X-rays can illuminate the ionosphere and cause what is known as an ionospheric disturbance,” said Peter T. Gallagher, professor of astronomy and astrophysics at the Dublin Institute for Advanced Studies in Ireland. News week.

“The ionosphere is used in radio-based communications to reflect or facilitate the transmission of radio waves. However, radio traffic can be interrupted if the ionosphere is disturbed by X-rays from a solar flare.”

The radio blackout on September 14 resulted in radio amateurs and sailors experiencing a loss of signal at frequencies below 30 MHz for up to half an hour.

The strength of the solar flare determines the extent of the blackout. Flares are classified into categories of A, B, C, M and X, with X being the strongest. At X4.5, this weekend's flare was one of the strongest. The strongest flare ever recorded was recorded in 2003 and estimated at around X45.

The CME, which was released at the same time as the X4.5 flare, is moving toward Earth and is expected to hit our magnetic field later on Monday.

“Periods of G3 [Strong] “On September 16, 2024, geomagnetic storms are likely due to influences from coronal holes and the expected arrival of a coronal mass ejection (CME) associated with an X4.5 flare at 14/1529 UTC from AR3825,” NOAA's Space Weather Prediction Center said in a forecast. “The aurora could be visible in the lowlands from Pennsylvania through Iowa to Oregon.”

Geomagnetic storms are categorized on a scale from G1 to G5, with G5 storms being the strongest and rarest. The G5 storm that caused auroras across much of the United States on May 10 was the first since 2003, during the same storms that triggered the X45 outbreak.

Charged particles in the coronal mass ejection are guided by Earth's magnetic field toward the polar regions, where they interact with gases such as oxygen and nitrogen, causing light emissions known as auroras. Stronger geomagnetic storms cause auroras to be seen at much lower latitudes than usual. The auroras take on different colors depending on the type of gas involved in the collisions, with oxygen typically emitting green or red light, while nitrogen can produce blue or purple hues.

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