Propagation News – 2 July 2023
The solar flux index stayed in the 150s and 160s last week, which is good news for HF propagation. From a flare and CME perspective, we have been lucky in that we have only had a few solar flares, all of which have been C- or M-class.
As a result, the Kp index has remained fairly low, being in the range of one to three after the rise to a Kp of five on the 25th due to the solar wind’s magnetic field, or Bz, tipping south.
We are, however, still in the summer doldrums, so daytime DX is limited thanks to D-layer absorption. We still recommend checking the bands at night as the MUF over 3,000km is still exceeding 14MHz and often reaching 18MHz at times. During the day Sporadic-E may still keep you entertained on the higher HF bands.
Daytime critical frequencies are around 5.2 to 6.7MHz according to the Dourbes ionosonde, which means you may find close-in contacts tricky on the 40m band at times, whereas more DX distances are still fine. Near vertical incidence skywave, or NVIS, 40m signals may not be returned to Earth with that critical frequency.
Looking ahead, active sunspot region 3354 was pointing directly at the Earth on Thursday, but has so far been behaving itself with mostly C-class flare events. It is still the most likely candidate for a coronal mass ejection, or CME, over the weekend.
Next week the Space Weather Prediction Centre has the Solar Flux Index declining to 130 before picking up later in the week to perhaps 145. The Kp index should remain around two, unless we have a CME which could see it rising to five with the attendant lowering of the MUF.
Meanwhile, you can get an idea of the best times to work various parts of the world by using the free Proppy software at soundbytes.asia/proppy or via VOACAP.com
VHF and up
The next week or so looks likely to continue in a very unsettled theme with low pressure residing over Scandinavia for much of the time and producing a west or north-westerly pattern over the UK.
This will mean that tropo propagation will not be a large part of our operations during the period ahead. On the other hand, the frequent spells of fronts with prolonged rain or heavy summer showers will make rain-scatter modes a good use of time on the GHz bands.
Talking of scatter modes, we are not in a major meteor shower at present, so random meteors are a good fail-safe although it can entail spending a lot of time in the process.
The solar conditions, as previously mentioned, can be unsettled at the moment, and thus there is a potential for radio aurora if the Kp index goes above seven or so, even though daylight makes visible events unlikely at this time of the year.
Lastly, the Sporadic-E situation is still our primary focus as we move into July. Days with good jet stream activity over Europe are good signs, whereas a high Kp index or solar flares are generally not so good.
Of course, there are many other parameters involved and one of the critical components is likely to be the random meteor count which shows how much meteor debris might be available to make the Sporadic-E patches. In a roundabout way, if you monitor the meteor pings you might get a feel for how the Sporadic-E prospects are stacking up.
The Moon declination is negative all week so there will be short Moon windows. Tuesday’s perigee means that path losses are at their lowest for the month. 144MHz sky noise is high this weekend but falling back to low levels by the end of the week.
Category: GB2RS Propagation News
