What are Solar Flares?

Solar flares are sudden, intense bursts of soft X-ray and EUV, 0.1–1 nm radiation from the Sun, triggered by the reconfiguration of magnetic field lines near sunspots.

A solar flare courtesy of NOAA, May 2023

When this energetic radiation reaches Earth it enhances the D-region of the ionosphere, causing "fadeout" and/or "radio blackout" events. Flares can last from tens of seconds to several hours.

Solar X-ray flares usually occur in active regions on the Sun, marked by strong magnetic fields associated with sunspot groups. The intensity of solar flares is classified based on peak emission in the 0.1 - 0.8 nanometes.

NOAA categorizes flares into different levels: A, B, C, M, and X.

Radio blackouts are classified using a five-level NOAA Space Weather Scale, directly related to the flare's max peak in soft X-rays reached or expected.

The severity descriptors for radio blackouts are as follows:

• R0 - Quiet sun
• R1 - Minor: Associated with "A" and "B" flares.
• R2 - Moderate: Associated with "M5" flares.
• R3 - Strong: Associated with "X1" flares.
• R4 - Severe: Associated with "X10" flares.
• R5 - Extreme: Associated with "X20" flares.

The correlation between the solar flare classification and radio blackout scale

Solar  Flare  Class	A	B	C	M		X
Radio Blackout Scale	R0			R1	R2	R3	R4	R5

The current solar flare

References:
1. Solar Flares (Radio Blackouts) ^{NOAA / NWS Space Weather Prediction Center}
2. Types of Space Weather Storms
3. Communications blackout ^Wikipedia
4. Radio Blackout ^UNDRR
5. Solar flare alert radio hams ^{Find on this site}
6. Solar flare alert warning ^{Find on this site}
7. Solar flares hitting earth today ^{Find on this site}
8. Solar flares today alerts warnings ^{Find on this site}