venerdì 24 settembre 2021

Propagation News – 26 September 2021

This week saw the Sun more active with up to five sunspot regions in place. Two of the regions are quite large, pushing the solar flux index up to 89 on Thursday with a sunspot number of 76. That should be enough to get the ionosphere up and running and we are also seeing early Autumnal HF propagation starting to take off.

Gary, G0FWX reports working Central America and the Caribbean on 10 metres, namely Venezuela, Puerto Rico and Surinam. Brazil has also been logged, but we are still awaiting widespread reports of North American stations to be logged on 28MHz.

Geomagnetic conditions have been variable with the Kp index hitting four on Wednesday, thanks to material from a coronal mass ejection. This sent the solar wind speed up to more than 400km per second and it was still above 300km/s on Thursday.

There has been solar flare activity recently and we can expect it to continue. This could mean sudden ionospheric disturbances and HF blackouts if the flare is strong enough and occurs during daylight hours. There could also be associated coronal mass ejections to contend with.

Next week NOAA predicts the solar flux index will remain in the mid 80s while the Kp index should eventually decline to two after reaching five this weekend. This is due to a coronal hole which is currently facing Earth. A high speed solar wind stream flowing from this zone should reach Earth later this week and contribute to a geomagnetic disturbance at higher latitudes.

VHF and up:

As predicted last week, we had a mix of weak Tropo and rain scatter modes, with an isolated report of the Cornish 10GHz beacon GB3MCB being copied for an hour by G4DBN in East Yorkshire at 460km overland.

This coming week the Tropo conditions will take a hit as low pressure becomes the dominant pattern for the coming week. This will take the form of active fronts crossing the country together with areas of showers, so at least there will be some rain scatter potential for the GHz bands.

At the moment, indications are that the return of any ridges, and hence Tropo, between the lows will be temporary and limited in scope, so best to think of other options like meteor scatter or aircraft scatter and possibly aurora to provide the unconventional modes this week.

There is one small meteor shower due to peak this week. The daytime Sextantids with a ZHR of five is due to peak on the 27th, but the timing of this peak is often uncertain. The maximum may occur even a day earlier than expected, so be alert and continue to check the early morning for the best random meteor scatter conditions.

EME path losses are at their highest this week with apogee today, Sunday, but with peak Moon declination coming up on Wednesday there is plenty of Moon visibility for Moonbounce enthusiasts. The Moon is at its zenith in the early morning. (