The optical propagation observed along the positive column of external electrode fluorescent lamps is shown to be an electron plasma wave propagating with the electron thermal speed of (kTe∕m)1∕2. When the luminance of the lamp is 10000–20000cd∕m2, the electron plasma temperature and the plasma density in the positive column are determined to be kTe∼1.26–2.12eV and no∼(1.28–1.69)×1017m−3, respectively.

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A new non-invasive method for the determination of electron drift velocity has been investigated by measuring the light propagation signals in external electrode fluorescent lamps with two usual operation methods. At the luminance of 12 000 cd m−2 with an operation frequency of 65 kHz, the electron drift velocity in accordance with the propagation speed of light emission is measured to be 2.72 × 105 m s−1. From the electron drift velocity, the electron temperature and the plasma density in the positive column are estimated to be kTe ∼ 1.6 eV and ne ∼ 4.3 × 1016 m−3, respectively, which agree well with data in the glow discharge plasma of typical fluorescent lamps.

The propagation velocity of a light-emitting wave-front is observed to be u p∼2×10+5 m/s before Townsend breakdown and u p∼5×10+6 m/s after Townsend breakdown along a discharge tube of inner diameter r o∼1.2 mm and length of 900 mm relevant to liquid crystal display television backlighting. Before Townsend breakdown, the origin of this wave is the ambipolar diffusion of plasma flux with the propagation speed u p∝D a/r o for the plasma bounded by the radius r o with the diffusion coefficient D a along the positive column. After Townsend breakdown, the light-emitting wave-front propagates with the electron plasma wave generated by the pulses of driving voltage. The electron plasma wave propagates such a long distance along the tube without damping due to the effect of localized plasma generation by electron impact ionization collisions. The propagation velocity is described by u p∼2u e 2/u d, which is larger than the electron thermal velocity u e as well as the electron drift velocity u d.