Planets can generate magnetic fields by vigorous convection of their molten, metallic cores. The mechanisms driving this convection, and the timescales over which planets are able to sustain an active magnetic field vary significantly for planets and asteroids within our solar system. Understanding the generation of these magnetic fields is essential for constraining the properties of the core, such as its thermal and electrical conductivity. Magnetic field signals can also be used to constrain the thermal evolution of a planet, including the time of differentiation and the onset of core solidification. The development of a stable planetary atmosphere may also be controlled by the presence of a planetary magnetic field, with significant implications for habitability.
My research investigates the magnetic field signals recorded by meteorites, lunar samples and early Earth materials. I combine a variety of experimental methods, including superconducting quantum interference device (SQUID) magnetometry and synchrotron X-ray photoemission electron microscopy (X-PEEM) to extract information about the intensity and direction of ancient magnetic fields. I also characterise the fundamental properties of magnetic carriers using electron microscopy methods, such as including electron backscatter diffraction (EBSD) in addition to micromagnetic simulations.
Bryson J. F. J., Nichols C. I. O., Herrero-Albillos J., Kronast F., Kasama T., Alimadadi H., van der Laan G., Nimmo F. and Harrison R. J. (2015) Long-lived magnetism from solidification-driven convection on the pallasite parent body. Nature 517, 472–475. Available at:http://dx.doi.org/10.1038/nature14114
Nichols C. I. O., Bryson J. F. J., Herrero-Albillos J., Kronast F., Nimmo F. and Harrison R. J. (2016) Pallasite Paleomagnetism: Quiescence of a Core Dynamo. Earth Planet. Sci. Lett. 441, 103–112. Available at: http://dx.doi.org/10.1016/j.epsl.2016.02.037 0012-821X
Harrison R. J., Bryson J. F. J., Nichols C. I. O. and Weiss B. P. (2017) Magnetic Mineralogy of Meteoritic Metal : Paleomagnetic Evidence for Dynamo Activity on Differentiated Planetesimals. In Planetesimals: Early Differentiation and Consequences for Planets Cambridge University Press, Cambridge. pp. 204–223. Available at: https://doi.org/10.1017/9781316339794