PMSE/NLC: more food for thought.

Yesterday saw extensive radar returns from mesospheric height above mid-Wales.  The physical 'thing' that this MST radar detects is ice - very small particles of charged ice that form around metallic meteor debris in midsummer, when the mesosphere is, seemingly paradoxically, at its coldest.  The individual ice particles are about the same size as the smoke in cigarette fumes - i.e., fractions of a micrometre, or the size of a modest bacterium.

Here's the plot from yesterday:

In the hours around midnight (27-28/6/19), there was a very extensive area of noctilucent clouds extending, visually, 120 degrees along the horizon.  Here is a stitched panorama of the view from north Wales at 23:44UT.  Incidentally, you can see the hills of the Isle of Man, 42km away, on the left of the sea horizon:

You can see, especially at the right, that the display was visible all the way to the sea horizon.  At zero degrees apparent elevation, the NLC is about 1200km away.  That's the latitude of central Iceland.  In fact, due to atmospheric refraction, it's likely to be somewhat further even than that.

So, this NLC was clearly covering a large area of the polar region, and is likely to have been covering most of the pole.  The daily AIM satellite 'daisies' show the typical extent, in this example, for midsummer's day (the satellite 'sees' at any illumination):

I did manage to fire a few FT8 'CQs' out last night on 24MHz, but I was reluctant to steer the Yagi from due east towards the north, due to very unseasonably high winds of over 60km/h.   Even so, my signal was heard:

The previous evening, there was no NLC.  When I sent the same signals at much the same time, no reports were returned.

More interestingly, perhaps, that this mid-late morning (28/6/19) saw several stations from Japan come through to western Europe.  I can tell the signals were arriving at low angles, because I have a low hill to my NE, and was entirely unable to get a signal across to JA, despite receiving some fairly strongly.  But MW0ZZK, a well-equipped station just a few km away from me, was merrily working several JA through the morning.

I think all this tends to suggest that some kind of organised, long-term campaign of relating higher HF and VHF openings to JA with mesospheric phenomena is well worthwhile.  I think we can be pretty confident it involves charged surfaces, waves, and multiple hops.  At least, that's my thinking...