The potential created by a current pulse is derived using a warm‐plasma description in the vicinity of the lower hybrid resonance (LHR). The results are somewhat different from the previous ones obtained with the cold‐plasma theory; the amplitude of the excited wave has an asymptotic decay with time ast−1rather thant−½. The spatial distribution of the potential shows a propagation effect that gives a reasonable explanation of the duration of the VLF echoes excited by the Isis 2 HF transmitter; it might also provide a technique for the measurement of the ionic thermal velocity and the drift velocity component perpendicular to the magnet