Solar CME and flares kill upper HF bands

Solar CME and flares kill upper HF bands

The last couple of days have shown both the good and the bad sides of increasing solar activity, says Steve G0KYA.

He adds that Sunday and Monday were fantastic examples of how high levels of solar activity/sunspots, coupled with quiet geomagnetic conditions, can make the bands come alive.

“The solar flux index was up to 190 on Saturday and geomagnetic conditions were relatively calm. All the upper HF bands, including 10 metres, were alive with signals on Sunday and Monday,” he says.

“At times it was difficult to know what to work, with 28MHz open to the east, south and west all at the same time. The USA was romping in – even 10m FM repeaters, some of which I haven't heard for years. Signals strengths were nothing short of fantastic.

“But oh dear, how that all changed on Monday evening.”

Steve says that the earth was hit by a double whammy. Just before noon UTC on Monday, the ACE Spacecraft detected a solar wind increase from 350 km/s to over 700 km/s at its peak.
A Coronal Mass Ejection (CME) swept past the spacecraft as a result of a long duration M class solar flare on Sept. 24.

As this hit the earth some time later the Kp increased to 8 on Monday evening and even local signals on 40m sounded fluttery.

“The double whammy was the solar flare activity with the result that the bands sound very, very flat on Tuesday,” Steve says.

“It may take the ionosphere some time to recover,” he says. “The CME will have depleted the ionisation and the flares will have increased D-layer absorption at the same time.”

Steve says that you can keep up to date with the current solar conditions at www.solarham.com.

“Ideally we want to see a high solar flux index, coupled with a low K index, and a Bz interplanetary magnetic field that points North (so reducing the coupling of CMEs into the earth's magnetic field). At the same time be wary of X-ray flares [detail on the site from the GOES satellite].

“The good times on 10m will be back, but it takes more than just a high sunspot number to make the bands really hum,” he said.


• Steve G0KYA and Alan G3NYK, of the Radio Society of Great Britain's (RSGB) Propagation Studies Committee, have released a free ebook called 'Understanding LF and HF Propagation'
http://www.southgatearc.org/news/august2011/propagation_ebook.htm

 

on the southern cross DX net this morning at 1100 UTC signals from VK are 20 over this morning , Go DX!

Jim
WU5E

 

What time is best from the West Coast?

Don
KF7QZB
Portland, OR

 

10 meters is great!

10 meters is great. I had no problems with 10 meters for about 7 weeks now. Talking to Greenland to South Africa to French Polynesia. Just gotta listen up...even the west coast is booming in. Glad to see the band open!

 

Let's not forget 12m....with many openings into Europe and elsewhere...it was really good last couple of weeks.



Gary
N5XED

 

I made my first psk qso on 10 yesterday useing 5w im loveing it!

 

Saturday was great on 10 Meters. It was almost like 1989 all over again. The high-latitude paths were wide open as I've not heard them for years.

Monday afternoon (East Coast North America), the high bands were still in fine shape. I went to cook dinner, and when I returned to the hamshack after a few minutes, I didn't hear a peep on 10 or 15 Meters. I thought that perhaps the neighbor's dog had chewed through my coax. But not so....

 

Saturday and Sunday were awesome on 10 meters. I was working both Europe and Austrailia along with Japan in the afternoon hours during the CQWW RTTY contest. On 9/28/2011 I worked FR1GZ on reunion Island also on 10 meters using JT65 at 10 watts. I am hoping there is still more fun to come on the higher HF bands after the storm calms down in Space. Now if we could only get 6 meters to open up like that it would be even better.
73
Bobby N4UPX