Propagation News

Solar data for the period from 30 May to 5 June -
compiled by Neil Clarke, G0CAS

Solar activity was low to moderate. Small M-class solar flares took place on the 1st and 3rd. A couple of small earthward-directed coronal mass ejections also occurred but nothing came of them. The solar flux increased from 93 to 105 by the 5th and the average was 96 units. The 90-day solar flux average on the 5th was 93, that’s one unit up on last week. Geomagnetic activity started at major-storm levels with an Ap index of 67 units on the 30th. This disturbance was associated with a coronal mass ejection a couple of days earlier. Activity quickly declined to ‘quiet’, although the 4th and 5th were affected by a coronal hole. The Ap index was 20 units on the 5th and the average was Ap 21 units. The ACE spacecraft saw solar wind speeds increase from 370 kilometres per second to 700 by the 5th. Particle densities were low and remained below 10 particles per cubic centimetre throughout the period. Bz fluctuated between minus 16 and plus 12 nanoTeslas on the 30th and between minus and plus 8 nanoTeslas on the remaining days.

The geomagnetic storm on the 29th and 30th resulted in degraded HF propagation but some excellent VHF auroral working, particularly on the 30th, when the event lasted through much of the day. 144MHz contacts were made well into Central and Eastern Europe, including Slovenia and Hungary. Good Sporadic E occurred on several days, mostly on 50 and 70MHz. Mostly notable was the 144MHz opening on the morning and afternoon of 1 June. The band was open to much of Europe, including contacts deep into Ukraine, presumably by double-hop - a relatively rare occurrence on this band.

The solar forecast. The quiet side of the sun is expected to be looking our way during the week of 12 to 18 June. Solar activity should be very low to low. The solar flux should decline and be in the 80s for most of the week. Geomagnetic activity is expected to be quiet to unsettled throughout. MUFs during daylight hours at equal latitudes should be about 20MHz for the south and 17MHz for the north. The darkness hour lows should be around 11MHz.

Paths this week to Australia should have a maximum usable frequency, with a 50 per cent success rate, of about 19MHz. The optimum working frequency, with a 90 per cent success rate, should be around 16MHz. The best time to try this path should be between 1000 and 1200UTC. A reminder that this month should bring the peak of the Sporadic E season. Openings are to be expected on most days. During the better openings double-hop contacts may occur at 50MHz with the Eastern Mediterranean and North America.

The RSGB propagation news is also available in a Saturday update, posted every Saturday evening and for more on propagation generally, see http://www.rsgb.org/society/psc.htm.

Source: GB2RS News - Courtesy of the RSGB

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