Friday, September 08, 2017

Severe geomagnetic storm as X9 flare CME arrives early

An early CME arrival is an energetic CME arrival, and this one didn't disappoint. A very pronounced sudden shock wave hit the magnetosphere yesterday (U.S. time). Boulder showed a classic sudden storm commencement. I have also read that Bz went as far south as -30 nT before moving back to the positive side.  Aurora was visible as far south as Arkansas. All this activity caused the K index to peak twice at 8. This is a severe storm (G4) condition.

HF propagation was pretty good at first, with 15 meter DX from this location until about 2000 local, but then conditions deteriorated considerably.  Currently, at 2100 UTC on the 8th, everything above 13 or so MHz seems pretty dead on this coast, though frequencies below that continue to propagate as well as can be expected.  HM01 (Cuban voice/digital numbers) is only down an S unit or so on 10715 kHz, and it is fading a only a little more than usual.

I wonder how close the hurricane is to the HM01 transmitting site, believed to be outside Havana.  It'll be interesting to see if HM01 stays up tomorrow.

Tonight may be decent for aurora again, in some locations, though the moon is still pretty bright.