Relationship between the energy distribution of electrostatic field change and lightning activity

A lightning strength parameter α (denoted as LSP or LAIDO), which is used for characterizing the phenomena of lightning activity, has been proposed, where α is defined by the characteristic energy obtained from the energy distribution of a radiated field component E in the electrostatic field changes produced by lightning discharge. Here, it is observed that the energy distribution of E_γ components is Maxwellian type. To prove more clearly the forementioned assumption from another viewpoint, changes of the amplitudes of the electrostatic field component E_S were measured and their distribution functions constructed. In the cloud-to-ground lightning discharges, the E_S components have a positive sign in the changes. However, those changes in the intercloud discharges are observed with either a negative or positive change depending on the distance between the striking point and the observation site. Therefore it is necessary to sum the numbers of occurrences of both positive and negative components for constructing an energy distribution of the E_S component. A fieldmill and a pair of doughnut-shaped electrostatic antennas are used in measuring the changes of the E_S component. As a result it is found that the changes of the amplitudes of the E_S components have a Maxwelliantype energy distribution. A characteristic energy β is defined which is obtained from the component of the electrostatic fields as a measure of LSP. Based on comparison of α and β it is clarified that β has the same characteristic nature with α. The lightning activity could be estimated from β.