AbstractThe radial temperature distributions in the central part of arcs burning through polyethylene (PE) tubes are estimated by measuring the half‐width ofHαline spectrum and using the electron density versus Stark half‐width and the electron density versus temperature characteristics. Estimation is carried out for various tube inner diameters (2 and 4 mm) and dc arc currents (5, 10 and 15 A). The result shows that the temperature at the arc center is around 10,000 K, and it tends to increase as the tube inner diameter becomes narrow and/or the arc current increases.The overall temperature distributions from the arc axis to the tube wall are obtained by combining these inner temperature distributions with outer temperature distributions which have been derived from C2spectra. They are found to take a form of typical two‐temperature distributions of ablation stabilized arcs.The electric field strengths of PE arcs are evaluated from the temperature distributions and the electrical conductivity versus temperature characteristics of thermally decomposed polyethylene vapor gas. The results agree well with experimental