Invariance of dynamo action in an early-Earth model.

Area of Science:

• Geophysics
• Earth Science
• Planetary Science

Background:

• Earth's magnetic field has persisted for at least 3.5 billion years.
• The geodynamo, responsible for magnetic field generation, was initially sustained by core cooling and later by inner core growth.
• Palaeomagnetic records suggest the geodynamo operated without a solid inner core for most of Earth's history.

Purpose of the Study:

• To investigate geodynamo action in the early Earth's core geometry.
• To understand dynamo mechanisms independent of fluid viscosity.
• To model magnetic field generation without a solid inner core.

Main Methods:

• Utilized numerical models simulating Earth's core dynamics.
• Employed early-Earth geometry in simulations.
• Tested dynamo action at extremely low fluid viscosity.

Main Results:

• Demonstrated geodynamo action independent of fluid viscosity.
• Simulations produced magnetic field intensity and morphology compatible with early Earth palaeomagnetic data.
• Observed remarkable similarity between early and present-day magnetic field simulations.

Conclusions:

• Fluid viscosity plays a negligible role in geodynamo simulations.
• The solid inner core may not be essential for generating Earth's ancient magnetic field.
• The findings challenge the role of the inner core in spatial-temporal variations of the present-day magnetic field.