MAGE

The MAGE model couples component models to create a holistic simulation of the geospace system. MAGE is being developed by the NASA DRIVE Science Center for Geospace Storms (CGS). More details about each of the components can be found at the MAGE model website.

To simulate the global magnetosphere, MAGE uses the GAMERA (Grid Agnostic MHD for Extended Research Applications) magnetohydrodynamic (MHD) model. To solve the MHD equations, GAMERA utilizes a finite volume method with high-order spatial reconstruction on curvilinear non-orthogonal grids. To maintain divergence-free magnetic fields to machine precision, GAMERA uses the constrained transport method. GAMERA is the successor to the Lyon-Fedder-Mobarry (LFM) model that was originally developed in the early 1980’s by John Lyon and collaborators. GAMERA uses the same numerical techniques as LFM, with some important improvements, but the software has been completely rewritten to adapt it to modern supercomputing technology.

For the inner magnetosphere component, MAGE uses the RCM (Rice Convection Model). The RCM solves a set of multi-fluid equations, whereby particle populations (electrons and ions) with different energy invariants are advected independently, to model the bounce averaged-drift kinetic motion of plasma in the inner magnetosphere. In MAGE, RCM is used to track pressure-bearing ring current ions that feed the “hot” pressure back to GAMERA. Additionally, some fraction of the total pressure is contributed by ring current electrons, which is also included. The RCM electrons also serve as a source population for ionospheric precipitation in MAGE. Finally, the RCM zeroth energy channel is used to track the motion of the cold plasmasphere which is included in the plasma density returned to GAMERA.

For the ionospheric conductance in MAGE, a completely new model has been developed, dubbed Dragon King. The current version of Dragon King includes mono-energetic and diffuse electron precipitation. Mono-energetic precipitation is derived using adiabatic theory relating electrostatic acceleration to field-aligned currents and thermal flux of the source population extracted from the model. The electron thermal flux is derived from the RCM in the inner magnetosphere and GAMERA at high latitudes, with a smooth transition between the two. Diffuse electron precipitation is derived by applying statistics-based wave-induced electron loss models to scatter the RCM electron population into the loss cone. The electron loss models are parameterized by the geomagnetic activity levels (Kp), the magnetospheric equatorial locations (MLT, L-shell) and particle energies. Once the combined diffuse and mono-energetic particlefluxes are derived, the Pedersen conductance is evaluated using the Robinson et al. (1987) formula and Hall conductance is derived from Pedersen conductance using the empirical ratio from Kaeppler et al. (2015).

For the high latitude electrodynamic calculation this version of MAGE uses the REdeveloped Magnetosphere-Ionosphere Coupler Solver (REMIX) model. REMIX solves the ionospheric Ohm’s law, i.e., the current continuity equation in a thin-shell approximation, to calculate the ionospheric electrostatic potential driven by field-aligned currents from GAMERA. Ionospheric conductance is computed by the Dragon King component as described above.

MAGE and its components are physics-based models developed to provide physical insight into various geospace phenomena. The MAGE development has focused on describing as much of the physics of geospace from first-principles as possible and minimizing the number of free parameters in the model. However, many caveats resulting from the complexity of the physics of the geospace system remain. These include poorly constrained initial or boundary conditions because of data sparsity, incomplete physics or parameterizations. Thus, the results are intended for scientific analysis, and the model has not been optimized for accurate space weather prediction during any specific events.

GAMERA:

• Solar Wind Input file in HDF5 format containing:
  • MHD state variables - density, velocity, temperature, and magnetic field vector
  • Date and Time
  • SymH
  • Kp
  • Dipole tilt angle
  • F10.7 solar flux
• Grid point location file in HDF5 format containing:
  • The X,Y,Z locations of cell corners in SM coordinates
• Run parameter file in XML format containing:
  • End time for simulation
  • Values for numerical parameters
  • Coupling parameters

• Same solar wind file as GAMERA component:
  • Date and time
  • SymH
  • Kp

Gamera outputs HDF5 files containing grid location, density, pressure, velocity vector, magnetic field vector and current vector.

RCM outputs an HDF5 file containing the time history of the full distribution for all three species, the electric and magnetic flux tube volume as well as auroral particle precipitation.

REMIX outputs an HDF5 file containing the locations of the polar cap grid points, electric potential, field aligned currents, Hall and Pedersen conductance, auroral particle energy and number flux.

Changed version to 0.75 for the early 2024 release for Run-on-Request without TIE-GCM. Patch level 1 (2024/03/10) includes minor corrections to the behavior of makeitso for single-segment runs and cda2wind.py's handling of missing KP or F10.7 data. Patch level 2 (2024/04/17) corrects compilation flags.

All users are strongly encouraged to contact the developers before publication or presentation of MAGE results obtained via the CCMC run-on-request service. The developers are happy to help the users learn how to apply the model correctly and interpret the results appropriately to ensure their scientific robustness.

A recommended citation for the MAGE 0.75 model is as follows: “The MAGE model is being developed by the NASA DRIVE Science Center for Geospace Storms (CGS). MAGE 0.75 (Sorathia et al., 2023) couples the GAMERA global MHD model of the magnetosphere (Zhang et al., 2019, Sorathia et al., 2020), the RCM model of the inner magnetosphere (Toffoletto et al., 2003) and the ionospheric electrodynamics model REMIX (Merkin & Lyon, 2010).”