Application of Low-frequency Magnetic Sensor for Remote Measurement of the Initial Continuous Current in Rocket-triggering Lightning

We present a new method to remotely measure the initial continuous current in classical rocket-triggering lightning using a compact low-frequency magnetic sensor deployed at 78-m distance from the channel base. The current waveform retrieved from the numerical integration of close magnetic signals shows very well the general feature and all the slow variations (such as the initial continuous current pulse) embedded in the channel base current measured with a shunt. Compared with the shunt measurement, the new method has the advantage of significantly reduced noise. This method can be applied to remotely probe the initial continuous current in upward lightning from high objects and altitude-triggering lightning, as well as long continuing current in natural cloud-to-ground lightning at a close range.