This is a Research Dataset associated with the manuscript submitted to

Geophysical & Astrophysical Fluid Dynamics (GAFD)


Title:

Sarwar A, Teed R, Simitev RD. "Dynamic force balances of bistable spherical dynamos with stress-free boundaries" [Data Collection]

Collection description:

Datasets to reproduce figures included of the research article  "Dynamic force balances of bistable spherical dynamos with stress-free boundaries" to be submitted for publication.

Funding: 

Science and Technology Facilities Council (STFC) [ST/Y001672/1]
Science and Technology Facilities Council (STFC) [ST/Y00146X/1]
Higher Education Commission (HEC), Pakistan [Ref: HEC/HRD/OSS-III/Batch-3]

ABSTRACT

Numerical dynamo simulations operate far from planetary parameter regimes, so comparisons rely on dynamical properties such as force balance. We examine whether force hierarchies are determined uniquely by control parameters in rotating spherical-shell dynamos with stress-free boundaries. Coexisting dipolar and multipolar attractors are tracked by continuation and analysed using force and force-curl diagnostics, with an emphasis on their time dependence during transitions and reversals. All simulations retain a leading geostrophic balance, while the next-order hierarchy varies between coexisting branches, including viscous--Archimedean--Coriolis (VAC) and VAC--magnetic (VACM) balances and differing Lorentz and inertial contributions. Time-dependent diagnostics show Lorentz--inertia reordering during a dipolar transition, but a polarity reversal occurs within a broadly unaltered hierarchy. Force curls reveal substantial viscous influence. On its own, magnetic morphology does not uniquely identify the underlying force balance.   

KEYWORDS

convection-driven dynamos, rotating spherical shells, force balance, bistability, time dependence


1) Data formats and software for analysis

The data are provided in ASCII comma-separated values (.csv) format and in the native checkpoint format produced by the Rayleigh pseudospectral simulation code.

The CSV files contain the globally averaged quantities and time-series data used to generate the figures. The checkpoint files contain the simulation states used to generate selected snapshots.

The simulations were performed using Rayleigh version 1.2.0 (Zenodo, doi: 10.5281/zenodo.11391213).

The data were analysed using Python, NumPy, Matplotlib, and the rayleigh_diagnostics tools.


2) Description of datasets

The dataset contains the numerical data associated with Figures 1--5 of the manuscript.


Data_fig01

* fdip_data.csv
* forces_and_curls.csv

These files contain the data used for Figure 1.


Data_fig02_fig03

* EnergiesAndForces_timeseries.csv
* SPH_Modes_selected_timeseries
* 02600000/
* 04500000/

The CSV files contain the time-series data used for Figure 2. The two Rayleigh checkpoint directories contain the simulation states used to generate the snapshots in Figure 3.


Data_fig04_fig05

* EnergiesAndForces_timeseries.csv
* SPH_Modes_selected_timeseries
* 09100000/
* 13500000/
* 18600000/

The CSV files contain the time-series data used for Figure 4. The three Rayleigh checkpoint directories contain the simulation states used to generate the snapshots of magnetic-field reversals in Figure 5.


3) Simulation parameters

The simulations are rotating Boussinesq convection-driven dynamo simulations in a spherical shell.

Ekman number, E:

* 1 x 10^-4
* 3 x 10^-4

Prandtl number, Pr:

* 1

Critical Rayleigh number, Ra_c:

* 65.11 for E = 1 x 10^-4
* 55.98 for E = 3 x 10^-4

The simulations include both dipolar and multipolar dynamo states.


4) Checkpoint data

The checkpoint files are provided in the native binary format generated by Rayleigh version 1.2.0.

The checkpoint files have not been converted to HDF5.
