Overnight WSPR Diary, 14-15/01/2018

Disturbed geomagnetic conditions to Kp=4 overnight, with moderate southerly Z swing, but large negative change in the X component:

Last USA spot was AD7QQ at 23:14UT, -26dB from 5W.  Again, I was the only dark side station to hear him (PY2GN was still too close to the grey line to include him in this result).  This was also the case for the penultimate USA spot of W7GBB, who was heard here ten minutes earlier.

AD7QQ reception reports, preceding 12h to 09:00UT 15/01/2018.

W7GBB reception reports, preceding 12h to 09:00UT, 15/01/2018

Then just a couple of G0 stations on groundwave, but with a few spots from SM until 00:24UT.

One DL/G6GLG spot at 00:58UT, -23dB from 5W.  Heard by several EU stations.

One spot from SV8LMM at 01:30, -13dB from 0.5W.  Heard also only by EI2GN 20 minutes later, at 01:50UT (roughly the time difference in longitude, which may or may not offer a hint in this particular case).

Two spots from ZB2GI, 02:50UT and 03:02UT, -24 and -27dB respectively, from 200mW.

Comment:

Clearly, there is some form of weak propagation regularly but intermittently available around the midnight hour to very early morning hours.  The field was not very disturbed at the time of the last USA spots, but the electron precipitation area on the antisolar point did lie directly to the north of the UK at the time.  This is a fairly consistent pattern that must be responsible for the latest spots here. 

But there is also something unusual about this QTH in consistently reporting unique spots overnight.  This is either down to (a) my low levels of RFI being so low that they are lower than practically anybody else's across the whole night side.  I find this plausible in respect of very many stations due to their concentration in developed areas, but unlikely in the case of all of nearly all of them or, (b) that the highly unusual mineralised ground conditions here are having some part in a very localised, minor enhancement that brings a few stations just within reach (although in the case of SV8LMM, the signal here was quite strong at -13dB, yet heard only by EI2GN and myself).

The SV8LMM spot coincided with an increase in the statistical aurora extent and field disturbance, as depicted below:

A run of VOACAP does, though, show that the circuit reliability to SV8 is actually a very good 30% at the time of the spot overnight, if we equate about 100W CW to be the same effective output as a 500mW WSPR signal (which is what SOTABEAMS, maker of WSPRlite, broadly claim (accessed 09:58UT, 15/01/2018)).

The SV8 signal's uniqueness in the UK remains difficult to explain.  But the fact that other EU stations didn't hear him is not, to VOACAP, surprising because of that quite good circuit reliability it corretly predicts.

This is what the reliability from SV8 to a receiver in northern Germany (similar latitude to me) looks like:

It's very different, having no circuit reliability at all after midnight (and not much in the very late evening).  Moving the receiver site around Europe, into Scandianvia, for example, yields the same absence of a nighttime circuit.

The question now to ask VOACAP is: what are the assumptions in the model that give this very reliable and location-sensitive match with reality?