Underground current impulses as a possible source of unipolar magnetic pulses

TL;DR

This paper models unipolar magnetic pulses observed near earthquakes as resulting from impulsive electric currents within the Earth's conductive crust, explaining their structure and common origin.

Contribution

It introduces a model of unipolar magnetic pulses based on magnetic diffusion from impulsive electric currents in the Earth's crust, unifying observations across different locations.

Findings

Unipolar magnetic pulses can be explained by electric currents in conductive media.

The pulse structure varies with measurement method and source characteristics.

The model suggests a common genesis for earthquake-related magnetic pulses.

Abstract

Recently several cases of observations of unipolar magnetic field pulses associated with earthquakes at different points (California, Italy, Peru) have been recorded. The paper attempts to model unipolar magnetic field pulses based on one mechanism that should be omnipresent for all measurement points, namely, the magnetic field diffusion through a conductive medium. The structure of magnetic fields supported by electric current sources is thoroughly modelled. The source of electric current is considered as an elongated volume of finite cross-section being immersed in a conductive medium. To model the unipolarity feature of the observed pulses prior to and at the earthquake main shock, the electric current of the source is of impulse form. Special attention is paid to the differences in the pulse structure (as amplitude envelope and the pulse width) that are measured by various magnetometers (fluxgate or search-coil). An analysis and comparison with recorded magnetic field pulse characteristics reveal that the observed unipolar pulses may have a common genesis, an electric current source within a conductive medium such as the earth crust.