On the origin of the lightning current oscillation measured at the Peissenberg Tower, Germany

Lightning currents with high-frequency oscillations have been measured on the top of the Peissenberg Tower in Germany. In 2007, the tower top section was replaced by a smaller construction. After the replacement, the frequency of the oscillation changed from formerly ~12.5 MHz to MHz. The pulsation was less significant for the currents at lower tower sections and for the nearby electric and magnetic field (~190 m from the tower). Calculations revealed that the oscillation is caused by the transient response of the top structure of the tower. The presence of the tower increases the risetime of the fast rising currents and limits the maximum current steepness. This might be the reason, why the highest maximum current steepness ever recorded did not exceed the value of 155 kA/μs.