Developing a Method to Determine Electrical Conductivity in Meteoritic Materials with Applications to Induction Heating Theory (2008 Student Thesis)

TL;DR

This thesis investigates a new method to estimate the electrical conductivity of meteoritic materials using induction heating, aiming to reassess magnetic induction's role in planetary formation despite measurement limitations.

Contribution

It introduces a technique to estimate the combined property of electrical conductivity and magnetic permeability in meteoritic samples, highlighting their importance in induction heating phenomena.

Findings

The method constrains the product of conductivity and permeability squared, ${\sigma}{{\mu}^2}$.

Electrical conductivity alone could not be precisely measured with this technique.

Magnetic permeability significantly influences induction heating in paramagnetic and ferromagnetic materials.

Abstract

Magnetic induction was first proposed as a planetary heating mechanism by Sonett and Colburn in 1968, in recent years this theory has lost favor as a plausible source of heating in the early solar system. However, new models of proto-planetary disk evolution suggest that magnetic fields play an important role in solar system formation. In particular, the magneto-hydrodynamic behavior of proto-planetary disks is believed to be responsible for the net outward flow of angular momentum in the solar system. It is important to re-evaluate the plausibility of magnetic induction based on the intense magnetic field environments described by the most recent models of proto-planetary disk evolution. In order to re-evaluate electromagnetic induction theory the electrical conductivity of meteorites must be determined. To develop a technique capable of making these measurements, a time-varying magnetic field was generated to inductively heat metallic control samples. The thermal response of each sample, which depends on electrical conductivity, was monitored until a thermal steady state was achieved. The relationship between conductivity and thermal response can be exploited to estimate the electrical conductivity of unknown samples. After applying the technique to various metals it was recognized that this method is not capable of making precise electrical conductivity measurements. However, this method can constrain the product of the electrical conductivity and the square of the magnetic permeability, or ${\sigma}{{\mu}^2}$, for meteoritic and metallic samples alike. The results also illustrate that along with electrical conductivity {\sigma}, the magnetic permeability {\mu} of a substance has an important effect on induction heating phenomena for paramagnetic ({\mu}/{\mu}0 > 1) and especially ferromagnetic materials ({\mu}/{\mu}0 >> 1).