"White Noise" on 20 meters

[k3xo]

I'd like to know if anyone knows about what I heard on 20 meters toward the end of the CQWW SSB contest last weekend.

On about 14.340, sometime between 2330 and 2400Z on October 31, I turned my beam north to about 350 degrees and I was trying to call a VE3 station. Just as the beam stopped there was a large increase in the level of background noise. It grew from a fairly quiet band to what I would call quite loud. I don't remember the S-meter reading, but it started to cover the VE3 which at the same time seemed to fade.

The noise did not seem to me to be man-made like line noise or other electrical noise, and it was not static from thunderstorms. It was a "pure" white noise and if you could describe noise as "granular", I would describe it as "fine".

Another way to describe it is like the wind coming up, although it was sustained rather than gusty. I could visualize some kind of ionospheric disturbance that might have been causing it.

I have heard this a couple other times recently on 10- or 15-meters.

Does anyone know what this noise is?

Rip K3XO