The Re‐magnetization of a Surface Outcrop by Lightning Currents

Abstract

Scattered directions of magnetization are commonly found in samples taken from surface outcrops in South Africa. An investigation of the directions of magnetization in samples from one outcrop of a Pilanesberg dyke combined with laboratory measurements of the remanent magnetism produced by d.c. fields and spark discharges showed that the pattern of magnetization in the outcrop was due to two horizontal electrical currents one of 5000 amps, the other of 50000 amps. These currents are almost certainly associated with lightning discharges. The effect of a.c. demagnetization in removing the magnetization produced by lightning is discussed. Copyright © 1961, Wiley Blackwell. All rights reserved