HF News
Last week was characterised by having a low Kp index, but an equally-low solar flux index.
The Kp index was predominately below two all week, thanks to a lack of Earth-directed CMEs or coronal holes. Unfortunately, that is about to change as we will explain later.
The solar index has been rummaging around the 100 mark, dipping as low as 93 on the eleventh and only as high as 105 on the sixteenth.
This has meant settled ionospheric conditions that have not been outstanding, but have at least been reliable. The MUF over a 3,000km path has reached 24MHz at times, often battling to reach 21MHz. This is a taste of things to come over the next few years as we descend towards sunspot minimum.
The settled conditions mean, however, that there has been DX to be worked. The CDXC Slack group reports FT8 and CW contacts with 3X3A Guinea on 17, 15 and 12 metres, 3B9G Mauritius on 15m CW and D60DX Comoros on 15 metres CW. Other DX includes 9V1DW Singapore on 17m and TN8GD Congo on 20m CW.
Now the bad news. A very large coronal hole on the Sun is rotating to be Earth-facing. A high-speed solar wind stream flowing from this zone is expected to reach Earth beginning April 17th. Active (Kp4) and minor (G1) geomagnetic storming may be possible this weekend. Expect reduced MUFs and poorer HF conditions.
DXpeditions active this week include V47EM St Kitts and Nevis, OX3LX Greenland, T31TTT Central Kiribati, TX9W Marquesas Islands and the continuing operations of D60DX Comoros and 3X3A Guinea.
NOAA predicts the SFI will climb next week, perhaps reaching as high as 145 by the 23rd. After the geomagnetic disturbances from the coronal hole die down we may then have two days or more of settled conditions before more disruption around April 25th, with a predicted Kp index of four – just in time for International Marconi Day!
VHF and up
The main note on the weather influence is that once high pressure becomes established at this time of the year it can be remarkably persistent. In this case the high pressure that is now developing over the UK may remain in control until the end of the month.
Tropo will therefore be a mode of choice, but a cool north or northeasterly flow over the eastern side of the country will mean that western Britain fares best for any lift conditions. Over eastern areas a cool northerly breeze will bring cloud and a few showers.
The prospects for aurora are still worth checking out by noting the Kp index for values above Kp=5, and preferably above Kp=7. As we reported earlier, a coronal hole and its effects may be reaching us this weekend, so check the Kp index and for fluttery signals on HF bands and get ready to turn your VHF beams northeast.
As for meteor scatter, we are now coming up to the peak of the April Lyrids on Wednesday 22nd and should see some activity increase to beyond the random fare of recent weeks. In contrast, rain scatter may not be a good option with high pressure or just isolated showers not offering much for the microwave bands.
We are rapidly heading towards May when the prospects for sporadic-E start to be worth checking. In the coming week there are not too many suitable jet streams, which can be good regions to look for Es. To get into practice for the new season check the Es blog on www.propquest.co.uk for a jet stream map and look for spikes in the foEs trace on the graphs. The site is currently being worked on, so apologies for any dropouts.
EME now, and Moon declination reaches a maximum high on April 21st. Moon perigee, its closest point to Earth, is on April 19th, so path losses will be at a minimum. Sky noise is slightly higher on April 21st, but this is minor and returns to low again on the 24th.