↑ What are Solar Flares?

This page is part of the project "Understanding HF Propagation."
by Doron Tal, 4X4XM

Solar flares are explosive bursts of soft X-ray radiation (0.1–1 nm), triggered by intense magnetic fields around sunspots.

Solar-flare
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 six-level NOAA Space Weather Scale, R0-R5. The correlation between the solar flare classification and radio blackout scale:

Solar  Flare  Class ↗ A  B  C MX
Radio Blackout Scale ↗R0R1 R2R3R4R5
Radio Blackout Scale:
  • 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 recent 3 days of solar flares | 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

The project "Understanding HF Propagation," focuses on skywave propagation,
shows near-real-time indices and explains what the terms mean.
Total visits since 17 August 2022.
Flag counter site maybe down!
Repeat visits counted as new after 24 hours.