Propagation News – 6 September 2020
This last week was characterised by unsettled geomagnetic conditions caused by an incoming high-speed stream for a solar coronal hole. We warned of this in last week’s report, but in view of the small size of the coronal hole, we didn’t really expect its effects to be quite so severe.
The solar material impacted the Earth on Friday, 28 August, pushing the Kp index to five. Unsettled conditions then persisted through until at least Wednesday, with the Kp index peaking at four on Tuesday, the 4th. Ionospheric HF conditions were adversely affected, with maximum usable frequencies over a 3,000km path struggling to get much above 14MHz at times. But by Thursday the Kp index was down to one and the ionosphere was recovering. At the time of writing, there are large coronal holes at the Sun’s poles, but any solar material may not be Earth-directed.
NOAA predicts the Sun will remain spotless next week, with a maximum solar flux index of 70. The good news is it has the Kp index at two, which could bode well for better HF conditions over the next seven days.
On another note, propquest.co.uk has a new NVIS tab on the foF2 graphs for a closer look at the prospects for inter-G nets on the lower HF bands.
VHF and up
This will probably be the final mention of sporadic E in the bulletin for this summer season. The coming week might offer some good opportunities from the jet streams, the main source of the turbulence that produces atmospheric gravity waves, so don’t rule sporadic E out just because it’s September.
With a low Kp index you might be able to get the odd FT8 path out of it, and even a chance of CW or SSB if you’re really lucky. Propquest.co.uk shows the daily jet stream maps and now we also have the sporadic E Probability Index, a single graphic to look at for hints of where the paths may occur.
We had some decent tropo over the last week, but it has temporarily suspended for now. Towards the end of Sunday a new high will build in from the Atlantic and, for much of the coming week, there should be some tropo chances as high pressure dominates. It’s looking like reverting to low pressure and wet weather by next weekend. The models are showing some heavy rain in some areas, so there is a potential for strong GHz bands rain scatter events.
Finally, autumn usually produces better chances of auroral propagation, and with the recently disturbed conditions, keep a check on the Kp index. Anything above four should attract attention. Aurora produces a very garbled distorted sound to SSB, so CW is best but wide-tone digimodes such as JT4G should work well. Beam north-east to the north-northwest and you could work stations via backscatter on 6m or 2m.
Moon declination is positive again, meaning longer Moon windows. This Sunday, the 6th, the Moon is at apogee so EME path losses are at their highest. 144MHz sky temperatures are moderate all week.
Just one small meteor shower this week, peaking on Wednesday, the September Epsilon-Perseids with a zenithal hourly rate (ZHR) of just five.
Category: GB2RS Propagation News
