Генератор Хаббарда

I’ve made a Hubbard-like coil with 7 wooden dowels and 20 AWG wire. The dowels measure 7 inches in height and about .75 inch diameter. I used 91 turns for each of the 7 and arranged them in the Hubbard style. Placing it nearby an ignition coil driven by a Joule Thief circuit, I see an unusual mutually inductive pickup that is regenerative and then damped.