Polar flutter on HF.

Whilst trawling through my old PC today, I came across this very clear example, from April 11, 2014 at 1951UT, of polar flutter on a 24MHz SSB signal heard in my 3-ele LFA Yagi.  Thanks to HRD's great audio logger and file creation, I can see that it was actually on 24.931.50MHz.

You can see from the image that, whilst the centre path of the signal was considerably south of a pass over the north geographical pole, it passed fairly close to the north geomagnetic pole - the pole that is a closest fit to a theoretical magnetic dipole as experienced at the surface. The signal crossed into an out of the auroral oval twice on its journey to me.

https://drive.google.com/file/d/1dWI-ExySmR0o-OWYrno2BPOL7j5oxA5j/view?usp=sharing

Likely path of KI7M's signal at the time.