1991 Volume 111 Issue 1 Pages 57-62
It is widely known that the measurements of an electrostatic component under a thunder cloud are useful for forecasting lightning discharges.
The measurement has been performed so far with the use of a fieldmill in the market. However, there are many problems in this; for example, weak time resolution, low sensitivity and many restrictions in the observation circumstances.
We have proposed a pair of doughnut shaped static antennas (denoted as a static antenna) for measuring the electrostatic component of the lightning discharges. But, we have not identified that the received signals through the static antenna really show the electrostatic component.
In the present paper we will clarify that the electrostatic component is measured correctly by the static antenna, after comparing the distance dependence of the electrostatic field and the radiation field component which is received with a CIGRE antenna. We have also confirmed this fact by observing the ratio of the output amplitude of the doughnut antenna to that of the fieldmill as a function of the distance between the struck points of the lightning discharges and the observation site.
The sensitivity of the present antenna is calibrated by using the fieldmill. It is revealed that the static antenna has many advantages in the measurements of a static field component in any weather conditions.