Propagation News – 13 September 2015

| September 11, 2015

This week the HF bands were once again plagued by the effects of the high-speed solar wind as a result of ongoing coronal holes on the sun.

The Kp-index hit six for more than 15 hours on Tuesday as incoming plasma caused a major geomagnetic storm. Listeners could be forgiven for thinking their receivers had broken as the HF bands were virtually devoid of signals. Wednesday was also very bad. The effects could be seen on the Chilton Ionosonde data as the calculated maximum usable frequency on Tuesday fell well below 14MHz. Recovery was slow with only 20m showing activity later in the day.

Autumn should herald the start of better HF conditions, but propagation is being dominated by coronal hole effects.

NOAA predicts that the solar flux index will be in the range 100-115 this week. The K index could suffer yet again from the effects of the high-speed solar wind, resulting in depleted F layers, lower maximum usable frequencies, strong solar absorption and auroral effects.

September is usually a good month for north-south paths, such as UK to South Africa and South America. In between geomagnetic events we should also see the lower bands becoming more usable too.

VHF and up propagation

The slightly lifted tropo conditions of last week will have subsided by this weekend as low pressure moves in, with unsettled weather in most areas, and quite windy conditions in the northwest at times. The only glimmer of hope seems to be that the models are indicating a return of high pressure near south-east Britain by the end of the week, so perhaps a slight improvement again for some areas by next weekend.

The sporadic-E season is all but done, although a few openings can occur on 10m. So as in the high summer, use the location of jet streams to guide you for these possible openings to make use of the dying embers of the 2015 Es season.

Last week’s VHF auroral conditions may have subsided for now, but keep an eye on the space weather for more activity. There are no major meteor showers this week so keep looking in the early mornings for the best random meteor scatter opportunities.

For EME operators, the moon is close to the sun today, making for more noise on the VHF bands. This week the declination goes negative with shortening Moon windows along with high losses as we approach apogee, the point where the Moon is furthest away from Earth, on Monday.

Category: GB2RS Propagation News