Propagation News – 25 July 2021
Sunspot numbers were down at the start of the week, but increased dramatically as the week went on. By Thursday the solar flux index was up to 94 with a sunspot number of 86. There were six active regions visible on the Sun. Although many of these sunspots were quite small and not very complex, they all contributed to the higher solar flux, which is now nudging 100.
The region that was active on its last rotation, 2835, and was responsible for multiple coronal mass ejections, appears to have quietened. Nevertheless, the Sun may well be more active next week as some of the regions have produced low-level C-class flare activity over the past few days. NOAA reports that solar cycle sunspot progression over the past several months has actually been ahead of the cycle 25 forecast. This may bode well for the future.
HF propagation remains dominated by Sporadic-E, with daily openings on the upper bands. F2-layer propagation is at seasonal levels, with openings up to 14 and sometimes 18MHz being recorded. We are not seeing much in the way of 21MHz F-layer propagation, but that will kick in as we head into Autumn. Thirty metres, or 10MHz, remains a band to check overnight with MUFs over a 3,000km path typically exceeding 10MHz.
Due to all this activity, NOAA has upped its forecast for the coming week. It now has the solar flux index at 85 next week, rising to 90. The geomagnetic prediction is for a maximum Kp index of 2, possibly due to a lack of coronal holes. However, it is too early to say whether we may have any solar flares and CMEs from the new regions currently rotating into view.
VHF and up
After some very good days of Tropo recently, it seems that the picture will look very different in the coming week. The decline of the high pressure will be complete by this weekend and heralds a week of unsettled weather with showers or longer periods of rain. On the upside, this puts rainscatter back on the agenda for the microwave operators.
Sporadic-E is still a good contender for DX although heading into August usually thins out the activity. The meteor input to E layer ionisation should keep hopes alive of renewed openings. The jet stream placements are mainly favouring the path to the south into Iberia initially, before moving east later to open up other more eastern parts of Europe.
Around we go again into another lunar cycle with negative, but increasing declination, this week. This of course means that we’ll see the Moon for longer as each day progresses. Declination goes positive on Thursday, but losses will rise daily after last Wednesday’s perigee.
Random or sporadic meteor rates are approaching their annual maximum around now, and the Southern delta Aquarids meteor shower is under way. This has a broad ZHR peak of 25 running from the 26th of July through to the 31st. Note that in Europe, the shower radiant is only above the horizon during the night and early morning. There are some other minor showers peaking next week, so we should see excellent meteor scatter conditions.
Category: GB2RS Propagation News
