[TAC] X-class Flare/HF Blackout

[Hank Kohl K8DD]

 From NA5N on QRP-L

Gang,
The sun produced another major flare tuesday afternoon, an X1.5 from
1919-1927 UTC. SEC/NOAA has not yet released the estimated velocity of 
the shockwave for determining when it WILL arrive at planet earth (not 
IF). The position of the flare, region 0808, is approaching the center 
of the sun, and at it's current position, we will receive pretty much 
the full blast from the shock wave. It WILL trigger a major to severe 
geomagnetic storm in about a day and half (like we're not used to that 
already this week!).

The energetic electron and proton data is also missing, since the 
instruments that measure this, such as the SOHO satellite, got thrown 
into saturation by this flare. The instruments are currently off line. 
However, ground-based instruments are showing very high attenuation to 
HF signals due to the D-layer. This means the D-layer definitely got 
highly ionized from the flare. There is an HF blackout in effect right 
now up to about 20MHz, which will likely begin to recover around 2300 UTC.

The good news, is once the D-layer begins to recover for normal HF 
propagation (about 2300 UTC), the D and E layers will remain extra 
ionized until local sunset. This will enhance skip propagation and the 
MUF will be raised, perhaps for 15M openings, until a bit past sundown. 
This leaves a little time for east coast QRPers to do some DX hunting, 
and a couple more hours for those on the west coast before the sun goes 
down. This temporary boost to the reflectivity of the D/E layers, 
combined with the normal gray-line propagation at sundown, could lead to 
some interesting DX on 20M and 15M (if open), including north-south paths.

Flares are definitely disruptive to HF propagation, but they do generate 
short windows of opportunity for good DX, such as described above. A few 
hours after a strong flare until local sundown is one of those windows.

Good DX,
Paul NA5N