HF News
Last week’s space weather was dominated by a large coronal hole on the Sun. This was probably one of the largest we have seen for many years.
Moderate (G2) geomagnetic storming was observed following the arrival of a solar wind stream from the hole, with the wind speed exceeding 600 km/s on Wednesday, the 26th. This pushed the Kp index to 6.33, depressing the MUF slightly.
Luckily, the daytime MUF over a 3,000km path mostly stayed above 28MHz, but it was slow to rise the next day, when it took until 0900hrs UTC to reach 28MHz. At the time of writing, the solar wind speed was in excess of 800km/s, so we can expect more disruption until at least Saturday 29th.
Meanwhile, the solar flux index declined to 152 by Thursday the 27th, with only four small sunspot regions visible.
CDXC members have been discussing working New Zealand (ZL) in the morning at the ZL sunset, often on low power. Listen/look for ZL4OL and ZL2CC, usually on FT8, but if conditions allow CW and SSB. Twenty or forty metres seem favourite, and the VarAC mode seems popular in ZL as well.
Next week, NOAA predicts the solar flux index will climb again, perhaps to 180 by April 4. However, unsettled geomagnetic conditions are forecast again, beginning on the 3rd. We may expect the Kp index to reach six, which may be the start of at least 10 days of disruption.
VHF and up
The overall picture for the weather patterns in the coming week is that of high pressure, which means that Tropo should be available as a good mode for VHF bands.
There can be quite strong temperature inversions in the region of large well-developed areas of high pressure and the best performance will usually be around the edges of the high where the height of the inversion and ducting layer is typically between 0.5km and 2km above the ground and can cover large distances for excellent DX prospects.
Occasionally, a shallow ducting layer can form near the ground overnight but often disperses by mid-morning. If you are in a good inversion region, try SSB or CW on the VHF/UHF bands, paths of up to 1,500km can often be achieved from a good ‘tropo lift’.
The reverse side of the high-pressure systems is that we will have low pressure nearby, mainly to the north and west of the UK. Any potential for rain scatter will mainly be over northwestern Britain, although an active front moving south on Friday March 28th, is a good candidate for chance rain scatter on the GHz bands.
The prospects for meteor scatter are still largely dependent upon random meteors, which are usually best in the hours before dawn. The solar activity continues to trigger auroral alerts – see the previous section for details of likely solar activity in this regard during the coming week.
Now onto Sporadic-E, and last week we had a few out-of-season isolated foEs ‘blips’ to between 5-7MHz, which was enough to produce propagation on 10m and 6m, albeit on a very fleeting basis.
There have already been some equinox-related 6m TE workable from the Southern part of the country, so keep an eye open late morning for Africa and late afternoon for South America
EME path losses continue to improve until perigee on the morning of March 30. Moon declination is still falling, reaching a minimum on Saturday the 28th. Moon windows will increase throughout the upcoming week. 144MHz sky noise is low apart from Saturday 29th when the Sun is close to the Moon in the sky, rising to moderate on Thursday before dropping back to low for the weekend.