Propagation News – 16 May 2021
Last week was a real roller coaster ride in terms of HF propagation. While the solar flux index remained in the 70s, we have had C-class solar flares and a coronal mass ejection that hit the Earth on the 12th of May. This ultimately pushed the Kp index to seven. It was largely as a result of the Bz component of the interplanetary magnetic field going sharply South, meaning the solar matter more easily coupled with the Earth’s magnetic field.
F2-layer maximum useable frequencies were impacted with the MUF over a 3,000km path falling to just over 14MHz for a time and there were widespread reports of visible aurora.
The good news is that Sporadic-E has been this week’s saviour, bringing lots of openings on 10 metres. As well as openings to Scandinavia and Europe, plus short-skip to Scotland, there were reports of openings to the Caribbean as well. It is hard to say whether this was multi-hop Sporadic-E, or an enhancement brought about by the geomagnetic disturbance.
And it wasn’t all FT8 for a change. Gary, G0FWX reported working Puerto Rico, Canada, USA, Paraguay, Western Sahara, Gibraltar, and Saudi Arabia on 10m SSB. This goes to show how 10 metres may be the band to be on this month.
Next week NOAA predicts the solar flux index will be in the range 70-84. Sunspot regions 2818 and 2821 will rotate into view next week, which may give the SFI a helping hand.
Geomagnetic conditions may be unsettled this weekend, with NOAA predicting a Kp index of five on the 16th. We may then have a few quieter days before it goes up again, due to coronal hole activity.
VHF and up
We had some very welcome Sporadic-E last week and, after the high activity closer to the peak of the Eta Aquarids meteor shower and recent lull early this week, Wednesday was boosted by an aurora. Contacts were reported to GM and GD on 6m in the afternoon and widespread Sporadic-E later in the day.
The overall weather contribution seems to suggest a repeat of the showery theme through to the end of next week. So once again good for GHz bands rain scatter. An obvious result of the low pressure and showery weather is a lack of Tropo conditions with no significant areas of high pressure on the current runs of the models.
Sporadic-E becomes more commonplace as we go through May and the usual advice is to check regularly throughout the day, but if time is limited, go for mid-morning and late afternoon/early evening. The stronger events could reach 4m and perhaps even 2m, particularly for FT8, but it is worth checking the other modes from now onwards. Since the position of jet streams in the weather part of the atmosphere can be good indicators of where Sporadic-E might occur, the prospects are looking good with a strong Atlantic jet stream across Spain and southern Europe, which means beaming to the south or southeast for best results. For the bigger stations, it’s also worth trying paths to the Caribbean and the north of South America on 6m in the evenings, since later in the summer the jet streams are not so well placed for this path.
With the Moon at peak declination this weekend, we’ll have long visibility windows and high peak Moon elevations. Path losses are falling as we are past apogee for the month.
No significant meteor showers this week so be active around dawn for the best random meteors.
Category: GB2RS Propagation News
