Searchlights for gravity and magnetics

Abstract

The development of mental schemata is important in developing an understanding of physical phenomena and processes. Gravitational and magnetic fields are often visualized by geophysicists as equipotential surfaces (for gravity) and field lines (for magnetics). In these cases, the schemata treat the geology as the source of the field. In seismic and electromagnetic prospecting, one instead visualizes a field that is emitted by the instrument. Example schemata are traveling wavefronts (seismic) and smoke rings (electromagnetic induction in the dissipative limit). I carried this instrument-focused conceptualization over to potential field prospecting by a schema, which envisages the instrument as a probe, illuminating the earth in a manner analogous to a searchlight. Different potential-field instruments (potentiometers, gravimeters, magnetometers, and gradiometers) each have different beam characteristics and consequently illuminate the earth in different ways. This schema provides a new way of visualizing potential fields in prospecting with applications in instrument development, data acquisition and processing, and interpretation.