Propagation News – 12 November 2017
As forecast, last week saw auroral conditions and the Kp-index rise to six as the result of incoming solar material from yet another coronal hole. The Aurora Borealis was even visible from northern England and Scotland. Coronal holes are lower-energy areas on the Sun with open magnetic field lines that allow tonnes of material to escape and form a high-speed solar wind. Very prevalent at this point in the solar cycle, every indication is that this phenomenon will continue at least until 2019.
The unsettled geomagnetic conditions were a double-edged sword. Maximum useable frequencies (MUFs) over a 3,000km path climbed to more than 28MHz as the solar material first hit on Tuesday. But by Wednesday, at times the ionosphere was struggling to support signals much above 14MHz over the same distance. This continued well into Thursday.
Next week, NOAA predicts that the total absence of sunspots may continue, with the solar flux index around the 70 to 75 mark. Geomagnetic conditions are predicted to be better than last week, but still unsettled at times, with a maximum Kp-index of three. This means MUFs may reach 28MHz at times, although 18 and 21MHz may be more reliable. However, there is evidence of more coronal holes on the SDO spacecraft’s extreme ultra-violet imagery, which suggests we have more of a bumpy ride than the NOAA figures predict.
For newcomers, this month continues to be a good one for long-haul DX on the higher bands so do keep a look out on 14MHz and above.
VHF and up
This Friday night and Saturday morning, 17 and 18 November, sees the peak of the annual Leonid meteor shower. The shower is active throughout November and, with a peak zenith hourly rate of 15, it is one of the larger showers of the year. The shower radiant—the point in the sky from where the meteors seem to emerge—lies in the constellation Leo. It occurs when the Earth passes through the debris left by the comet Tempel-Tuttle. Use your favourite search engine to find the DL1DBC Virgo real-time meteor prediction page to find the best time and beam directions to work meteor scatter on VHF using this shower.
It’s hard to get too excited about the prospects for tropo over the next week or so, apart from a chance of some weak high pressure over the southern half of the country. This may not amount to much of a lift for VHF operators, so that just leaves us with some options for rain scatter on the GHz bands. This will, like previous weeks, be due to heavy showers that form over the seas around the British Isles at this time of year. They are worth seeking out both day and night—just follow the bright echoes on the weather radars.
Moon declination goes negative at moonset on Tuesday and losses are climbing this week. There is still plenty of time for EME contacts this lunar cycle before the Moon gets to apogee, its furthest point away, and its maximum southerly declination on Tuesday, the 21st.
Category: GB2RS Propagation News
