Overnight WSPR report, 2019 January 25-26

Raul, LU8DPV, started transmitting 5W 14MHz WSPR before midnight last evening, just in time to reveal an interesting variation in signal strength in the depths of solar minimum, midwinter night:

This is how the Z component of the geomagnetic field varied last night:

The peak at 00:04UT in LU8DPV's signal correlates nicely with a rapid northerly deviation in the vertical component.  The trough in the signal seems to correlate well with a recovering field after a minor south-going rebound at around 01:00UT.  The second peak at 02:00UT does not correlate with any particular event, when the field was slowly undergoing a restoration to quieter levels.

The most interesting aspect of the signal is perhaps not the variations, which are generally explained quite well by a changing field, but the fact that LU8DPV was the only station, apart from the very short-skip G0CCL and one or two other, short skip European stations, that I heard overnight:

G0CCL's signal, though not heard very frequently, reappeared and also tended to show the same peaks at 00UT and 02UT (blue vertical lines).