Overnight WSPR report - 06-07 January, 2019

Before going to bed last night, I checked my laptop was running the SDR receiving software at 14MHz properly.  As usual, it was.

But I noticed that F1AGR was coming in as a very bright line on the waterfall.  With only 1000km between us, and only 100mW out, the signal was hitting positive signal to noise ratios for some time around midnight (vertical blue line):

This is certainly unusual, as geomagnetically quiet periods typically result in no, or possibly only occasional spots from F1AGR during the midnight period.  The beautifully coherent rise, peak and fall of the curve might well suggest the cause of the propagation was geomagnetically-induced Es from electrons precipitating from the daytime hemisphere.

Image: Tromso Geophysical Laboratory

The field was slightly disturbed (peak Kp ~4), with the spots from F1AGR reaching a peak strength at the same time as the Z deflection was at its deepest southerly swing at Arctic Circle latitude.  Unfortunately, data is not coming in properly from several instruments at present, so it is not easy to relate propagation to field conditions.

One spot from 5W by LU8DPV also anomalously appeared at 22:56UT, at a strong -11dB SNR/2500Hz.  Unfortunately, LU8DPV seems to have only sent one transmission, so explanation is rendered rather more difficult than it already is.  Even so, a great circle path seems very unlikely.

Also very unusually, HZ1AM's 200mW was heard for an hour and 20 minutes from just after midnight, and then vanished for some six hours until his usual reappearance with the advancing morning:

Much the same was true of HZ1SK.  Again, I suspect that geomagnetically-induced Es is the explanation here, but quite why these stations are 'selected' for reception when so many others are also potentially available, is quite a mystery.