Fluorescent Lamp Oscillator

[Ultralume]

Does anyone know why a fluorescent lamp run off DC with a simple resistor ballast creates an oscillation anywhere from 1500 to 2800 Hz ? You will see a small sine wave a few Volts p-p across the lamp with a DC blocked scope. The bulbs that do this are 4W-20W linear bulbs and 22 W circlines as well. Two small bulbs in series will both oscillate at their own frequency creating a beat note. I've asked this question before on other forums and no one seems to know why?

 

[brickbat]

One possibility: you're creating a 'relaxation oscillator'. Google it, you'll see...