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Propagation News – 1 August 2021

Last week the Sun was bursting with sunspots, with a solar flux index in the high 80s. But, by Thursday, we were looking at a different picture, with zero sunspots and a solar flux index of 79. We also had a geomagnetic disturbance, thanks to the arrival of a high-speed stream from a coronal hole late on Wednesday. This pushed the Kp index to four, with the solar wind speed remaining elevated until at least late Thursday. The disruption triggered a short-lived ionospheric enhancement, with maximum usable frequencies over a 3,000km path reaching 25 MHz at 20:40 UTC on Wednesday, according to Propquest and the Chilton Ionosonde data. But, by Thursday morning, MUFs were struggling to reach 14MHz.

Propagation earlier in the week had been quite good, with extensive openings to the Far East on 17m. Rodney, G0CBO reports working a host of stations, including Japan and Kazakhstan, using just 40W FT8 to a vertical. Steve, G0KYA worked 8N8OLP, the Tokyo special event station for the Olympics, using 50W FT8 to a quarter-wave vertical on 20m.

Next week, NOAA’s Space Weather Prediction Centre predicts the solar flux index will remain in the mid-70s. It also has the Kp index at a maximum of two or three, reflecting the lack of solar coronal holes. There is the possibility of a geomagnetic disturbance this weekend caused by material arriving from a small coronal hole on the Sun’s equator, but its effects are likely to be minimal and short lived.

VHF and up:

Last week provided some excellent rainscatter QSOs for GHz bands operators. The heavy showers across the South and East of the country coincided with not one, but two GHz contests. During the all-day Sunday, UK Microwave group event, many stations reported working into the North of England from the South and East Anglia via backscatter from a line of heavy showers extending from Ipswich down to Southampton.

The coming week looks very similar to the last one, with an unsettled weather pattern offering further heavy showers or thunderstorms and longer periods of rain. This will favour rain scatter, while there is little prospect of any high pressure systems returning to produce Tropo.

Regarding Sporadic-E, the unsettled weather suggests there will be jet stream activity to help along any late-season interest. Remember that the season can extend into early September, so plenty of time to fill in any missing squares this year.

With positive Moon declination, this week we’ll have long Moon visibility windows, but with apogee on Monday, path losses will be at their highest.

Random or sporadic meteor rates are still high, but there’s a big shower on the way. Get ready for the largest shower of the year, the Perseids. This peaks on the 12th and 13th of August with a zenithal hourly rate of 100. Find out more about this shower next week. (rsgb.org)

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