Formation of current coils in geodynamo simulations

Area of Science:

• Geophysics
• Computational physics
• Earth science

Background:

• The geodynamo, responsible for Earth's magnetic field, is complex to simulate due to extreme core conditions.
• The Ekman number (E) quantifies simulation realism, with core conditions near E = 10(-15).
• Previous simulations achieved E down to 10(-6), but realistic parameters remain challenging.

Purpose of the Study:

• To perform a geodynamo simulation at an unprecedentedly low Ekman number (E ≈ 10(-7)).
• To investigate the impact of high resolution on geodynamo simulation results.
• To explore novel convection and magnetic field structures at near-core conditions.

Main Methods:

• Utilized the Earth Simulator with 4,096 processors for high-resolution computation.
• Conducted direct numerical simulation of the geodynamo process.
• Analyzed convection flow and magnetic field generation at E ≈ 10(-7).

Main Results:

• Achieved the lowest Ekman number simulation of the geodynamo to date (E ≈ 10(-7)).
• Observed qualitatively different convection patterns: sheet plumes/radial sheet jets instead of columnar cells.
• Identified effective dynamo action with current organized in helical spring or toroidal structures.

Conclusions:

• High-resolution geodynamo simulations reveal new physical regimes.
• Sheet plume convection is an effective mechanism for generating magnetic fields.
• Findings advance our understanding of the geodynamo and Earth's magnetic field generation.