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Propagation News – 2 June 2019

A couple of small Earth-facing coronal holes were the source of an elevated solar wind stream that pushed the Kp index to four on Wednesday. Otherwise solar conditions were generally quite flat last week. This helped sporadic E production, which saw 10 metres come alive, with the band sounding more like 20 metres on a good day. Unfortunately, this came to an end midweek when the Kp index soared, as we’ll explain later. One highlight was the start of the Cricket World Cup, with special stations GB19AUS, for Australia, and GB19LL, for Lord’s London, starting the ball rolling on Thursday.

The Sun remained distinctly spotless and that trend is due to continue. NOAA predicts more of the same with the solar flux index between 68 and 72 next week. The good news is that geomagnetic conditions should remain quiet with a maximum Kp index of two forecast over the next seven days. This should help the ionosphere replenish itself.

This weekend has seen National Field Day take place and while we can’t say how conditions have been, we are sure that there have been the odd instance of DX openings, albeit fleetingly. This is an example of how you can write off a band, only to find it opening up in one direction for 10 minutes or so. F2-layer openings do occur on the higher bands, even at sunspot minimum—it is just a case of being lucky enough to catch them.

VHF and up:
There has been some spectacular sporadic E across much of Europe during the last week or so, reaching up to 144MHz in a few cases. However, this changed from midweek as conditions reverted back to normal and sporadic E barely made it to 10m.

So what changed? Well, on Wednesday the Kp index was four at a critical time when sporadic E might form. This is higher than ideal; typically a K-index of less than three is good. Also there has been a gradual deterioration in the positioning of the jet streams in the upper air and these look to be less likely to intersect with the Alps or Pyrenees as we move through this weekend. Sporadic E paths into Europe may well be biased towards northern Europe, the Baltic and Scandinavia.

Regarding other modes, we appear to be lined up for being associated with low pressure and a showery weather pattern, so offering the prospects for rain scatter on the GHz bands. Watch out for thundery showers today. High pressure does try to return at the end of the week, but may not bring strong tropo, although sea paths around Britain may offer the better paths.

The Moon reaches peak declination on Wednesday and perigee on Friday, so a good week for EME with long Moon windows and low path losses.

Next Friday and Saturday sees the peak of the daytime Arietids meteor shower, with a zenithal hourly rate of 30.

rsgb.org

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