Capacitive discharge

This long-exposure shot was taken in my lab after work hours, with all lights switched off to show a very elusive phenomenon (the red and green illumination comes from indicator lights around). The object of interest here is a fluorescent batten which is also switched off, but which shows some unmistakable light emission at the extremities of the 36W fluorescent tube inside. This phenomenon is caused by capacitive current leaks in the circuit which arises from the AC mains (50 Hz) combined with parasitic capacitances in the cables and between the lamp and its grounded luminaire. Very weak discharges are thus fed around the electrodes, in the tube's argon-mercury Penning mixture, driven by the non-negligible electric field present around those electrodes. From the picture, it is clear that the right electrode is fed with more parasitic current than the left one.