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/aug…tion_ebook.htm
