Propagation News – 5 March 2023

| March 3, 2023

The auroral event last week was probably the strongest we’ve had in this solar cycle. There were widespread visible aurora reports from the UK on Sunday, 26 February. The Kp index eventually hit seven at 0900UTC on February, the 27th, sparking widespread visible aurora alerts all over the UK for Tuesday evening as well.

The solar wind speed gradually decreased to below 650km/s and the Bz component of the interplanetary magnetic field shifted to the north, bringing the Kp index down.

March is always a good, or bad, month for aurora, depending upon your perspective. The aurora is at its most active around the equinoxes in March and September.

Active region 3234 also produced an M8.6 flare on the 28th, but as this was at 1750UTC, the radio blackout was restricted to the Americas. Any CME material was directed away from Earth.

The solar flux index remained in the range of 150 to 160 last week, which was enough to make the daytime maximum usable frequency remain above 28MHz most of the time, although the geomagnetic disturbance did have an effect and lowered it slightly.

Next week NOAA predicts the SFI will remain in the range of 145 to 165. A geomagnetic disturbance is predicted for the fifth to the seventh, which could see the Kp index hit five. So, watch out for visible aurora once again.

The period between the 9th to the 14th is predicted to be generally calm geomagnetically, so this might be the best time for DX on the upper HF bands.

However, as we know this is a difficult time for predictions, anything could happen. We suggest keeping an eye on solarham.net for updates.

VHF and up

The very strong high pressure and tropo enhancement recently have competed for attention with magnificent auroras, but we are now heading into quieter territory. The large high will decline early this weekend bringing an end to the tropo bonus.

After which, the main weather theme is that of a colder northerly weather type with wintry showers, especially near windward coasts. This raises the prospect of rain scatter on the GHz bands.

After the recent dramatic solar-induced propagation week, it would be optimistic to expect a repeat, but the spring months are notable for producing auroras and there is always random meteor scatter. So, there are plenty of options to check up on in the coming week.

For EME operators, Moon declination is still high this weekend but we are on the downward trend, turning negative on Thursday, meaning Moon availability windows shortening all week.

With perigee last Friday, path losses will continue to fall. 144MHz sky noise is low all week. Perhaps you already view your radio activity in the context of propagation conditions. But, for those not yet making this a routine, becoming aware of how these things are controlled can make a huge difference to your operating successes.

Why not start by seeking out some of the excellent propagation talks from radio clubs and the RSGB Convention which are often available online?

Category: GB2RS Propagation News