This month let’s continue our foray into space weather and its impact on HF propagation. Over the past two months, we’ve scratched the surface of HF (high frequency) DX (long distance) propagation by examining great circle pathways, auroral circles, radiation, geomagnetic storms, sudden ionospheric disturbances (SIDs), coronal mass ejections (CMEs), and radio blackouts. These events result from “space weather.” Our Sun is the origin of “space weather.” Space weather impacts our Earth’s magnetic field and our ionosphere. Earth’s ionosphere and its magnetic field are closely related. Impacting one will influence the other, which in turn impacts — yep, you guessed it — our HF propagation.
Solar Indices
This month we’ll focus our attention on SSN (smoothed sunspot numbers), SFI (solar flux index), and A and K solar indices to finish our three-part delve into space weather. I’ve found taking a quick peek at SSN, “A,” and “K” indices gives me a fast, “shorthand,” nearly0-realtime glimpse into solar and HF propagation conditions I can expect for the day. However, for me to get to the point of understanding the potential HF implications of these solar indices, I first needed to become acquainted with their overreaching impacts.
Over the past two months, this column’s space weather topics can be thought of as a
