PROPAGATION
So far, Solar Cycle 25 is outpacing the official predictions as we saw in April, which excited the ham radio community as the 10.7-cm radio flux daily readings peaked at 160, breathing life into the higher bands of the shortwave radio spectrum (also known as HF, for the high frequency segment of radio spectrum [3-30 MHz] –ed).
Some spectacular moments occurred in April, including the strongest X-ray flare, which measured X2.2 (See scales in Figures 1a, 1b, and 1c), peaking at 03:57 UTC (Coordinated Universal Time) on April 20th. This erupted from a sunspot region, numbered as Active Region (AR) 2992, that was just rotating out of Earth’s view yet caused a radio blackout over the sunlit area of Earth, mostly over Asia during those hours.
The effects from a solar flare arrive in approximately 8 minutes because the emissions from the flare travel at the speed of light. If a flare erupts and triggers the ejection of coronal mass plasma, it results in a Coronal Mass Ejection (CME). If the CME is directed toward caused an R3-level radio blackout (also known as a Sudden Ionospheric Disturbance, or SID). They can last from 10 minutes to several hours <>.
