Propagation News – 26 February 2023
Last week was characterised by many low- and medium-level solar flares. At the time of writing, in the past seven days the Sun has emitted more than 60 C-class flares, six M-class flares and one X-class flare.
The X-class flare coincided with the measurement of the solar flux index meaning an erroneous reading of 343 was logged. The next day it was back to a more accurate 167.
The solar flux index has generally declined from the 200s we saw earlier in the month and stood at 152 on Thursday 23 February. Nevertheless, daytime maximum usable frequencies over a 3,000km path still exceed 28MHz on a daily basis.
Geomagnetic conditions have been mixed with the Kp index hitting 4.67 on Thursday due to a fast solar wind.
We are heading towards the equinox period as we leave February next week and enter March. This is a time that favours North/South paths, such as the UK to South Africa and UK to South America.
We’ll start to lose propagation to the USA on the higher bands as the Spring progresses, but don’t worry – it will be back in the Autumn!
A coronal hole is turning into an Earth-facing direction, which may cause some disruption with an increasing Kp index this weekend.
NOAA also predicts slightly worse conditions for the next week with the solar flux index declining to the 125-145 range. Unsettled conditions are predicted for the period of the 5 to the 7 of March, with the Kp index perhaps hitting five again.
As always, this is a guide as we are living in unpredictable times with regard to solar activity.
VHF and up
The coming week looks likely to be another high-pressure period on the weather charts. As we ended this week, the high was offset to the west of Ireland, but will become centred over Scotland with a colder north easterly over southern Britain.
This means that Tropo may become a mode of choice, particularly for northern areas, although this may well decline as a colder northerly starts at the end of next week. This could offer rain or snow showers with the chance of some associated GHz band scatter propagation.
As secondary options, aurora and meteor scatter remain viable, of course. Watch for a high Kp index for aurora and remember that random meteor scatter is always likely to be best around dawn.
For EME operators, the positive and rising Moon declination this week will see Moon availability windows lengthening until maximum declination on Wednesday. So, there will be high moon elevations, but path losses will continue to increase until apogee next Friday when the path loss trend will reverse.
144MHz sky noise is moderate to low for the rest of the week, only reaching 500 Kelvin on Tuesday and Wednesday.
Category: GB2RS Propagation News
