Auroral buzz

VA2BBW sent me this file, recorded by him during an SKCC QSO with me on 10m. The QSO took place on 2023-09-25 at 1353z, while Ante was operating as VC3K/VE2 in the SKCC Canadian Straight Key Month event. Normally, 10m is yet to open here at that time, but VA2BBW was a solid S5 here in Colorado, while he gave me an honest 599.

I believe that the QSO was enabled by a burst of auroral activity; the aurora was probably being modulated by the North American electric grid at 60Hz; as we can see from this spectrum plot (taken from the elongated dah in the "d" of "de") the raspy buzz is clearly due to 60Hz modulation.

This is the first time I have heard such a manifestation; normally, auroral QSOs that I have heard display distinct widening of the signal, along with blurring of the individual CW elements as different parts of the auroral region move around at different speeds.

Or to sum it all up in three words: radio is magic.