Close-range electric fields associated with lightning strikes to the austrian Gaisberg tower

We present measurements of very close vertical and horizontal electric fields from leaders and return strokes associated with lightning strikes to the 100-m tall Gaisberg tower in Austria obtained in 2007 and 2008. Simultaneously with the fields, return-stroke currents were also measured at the top of the tower. The vertical electric field waveforms appeared as asymmetrical V-shaped pulses. The initial negative electric field change is due to the downward leader and the following fast positive field change is due to the upward return stroke phase of the lightning discharge. The horizontal (radial) electric field due to the leader phase has a similar waveshape to the vertical electric field. However, the horizontal field due to the return stroke is characterized by a short negative pulse of the order of 1 microsecond or so, starting with a fast negative excursion followed by a positive one. Due to the shadowing effect of the tower, the returnstroke vertical electric field changes appear to be significantly smaller than similar measurements obtained using triggered lightning