TIEGCM v3.0

The NCAR Thermosphere–Ionosphere–Electrodynamics General Circulation Model (TIEGCM) is a comprehensive, first-principles, three-dimensional, non-linear representation of the coupled thermosphere and ionosphere system that includes a self-consistent solution of the middle and low-latitude dynamo field.

It is developed and maintained by the High Altitude Observatory at NCAR.

Contents

• Quick Start
• Repository Layout
• What's New in v3.0
  • New Features and Functional Changes
  • Changes in Physics
• Data Files
• Utility Tools
• Documentation and Support
• Citation
• License

Quick Start

For a brief set of instructions to build the model and make a short default run, see the TIEGCM documentation. The recommended path is via TIEGCMrun, a Python tool that automates compilation and execution.

Note: Download the input and supporting data files before building or running the model.

Repository Layout

Subdirectory	Description	Summary of Contents
scripts/	Support scripts	Job scripts, Make files, utilities
src/	Source code	Source files (*.F, *.F90, *.h)
tiegcmrun/	TIEGCM user interface	Python tool for pre-processing, build, and job execution

What's New in v3.0

This is a summary of modifications made to TIEGCM since the release of v2.0.

New Features and Functional Changes

• Flexible resolutions — the job script supports arbitrary combinations of horizontal and vertical resolutions; magnetic-grid changes are also supported.
• Extended upper boundary — the job script, defs.h, and several altitude-dependent variables (xfac, ar_glbm, aureff, bdriz) have been rewritten to support raising the upper boundary.
• High-cadence model time — input/output timestamps are now 4 digits (day/hour/minute/second) instead of the old 3-digit format (day/hour/minute).
• Unified N2 / MBAR / SCHT calculations — the N2 mixing ratio, mean molecular mass, and scale height are computed once and shared. Artificial caps on the N2 mixing ratio have been removed.
• Rewritten Helium module — included at all resolutions (default on); Helium effects on heating rates and elsewhere are now accounted for consistently throughout the code.
• Ring filter — replaces the old Fourier filter.
• O+ sub-cycling — controlled by a new input parameter NSTEP_SUB.
• NetCDF4 parallel I/O — reduces memory usage on the root task.
• Bit-for-bit reproducibility — ESMF calls have been modified to ensure reproducibility.
• Updated IGRF — the geomagnetic field is updated to the latest International Geomagnetic Reference Field.
• Rewritten magnetospheric coupling module — supports in-memory MPI data transfer.
• MPI subroutine optimizations — several MPI subroutines have been rewritten for a speed boost.
• Consistent dipmin calculation — set to sin(dlat*2*dtr) instead of being manually set per resolution.
• Code simplifications — unused parameters, arguments, and variables removed from some functions.
• Miscellaneous bug fixes.

Changes in Physics

• Solar heating coefficients — modified (Astrid Maute).
• Height variation of equatorward electric field — a scaling factor is added to account for the height variation of elam (Astrid Maute).
• Field-aligned ion drag — now included in the momentum equation (Jiuhou Lei).
• Collision frequency — lamdas.F now includes all ion species (O+, O2+, N+, N2+, NO+) instead of just O+, O2+, and NO+ (Haonan Wu).
• N(2D) transport — the minor-species solver now includes N(2D), previously assumed in (photo)chemical equilibrium; affects N chemistry at very high altitudes (z > 7) (Haonan Wu).
• Electron heat flux parameterization — the parameterization of fed near the equator is changed in settei (Tong Dang, Wenbin Wang, Kevin Pham).
• O+ number flux parameterization — the parameterization of opflux near the equator is changed in oplus (Haonan Wu, Wenbin Wang).
• Thermal electron heating efficiency — a sixth-order polynomial is now used (Yihui Cai).
• Electrojet turbulent heating — included, default off (Jing Liu).
• Empirical SAPS — included, default off (Wenbin Wang).
• Eclipse solar EUV masking — support added (Tong Dang, Jiuhou Lei).
• Lower-boundary forcing by external data — SD nudging support added (Haonan Wu, Xian Lu).

Data Files

The input and supporting data files required for TIEGCM v3.0 are available here:

• TIEGCM Data Files

These include the datasets needed to run the model and support various configuration options.

Download and place these files in the appropriate location before building or running the model.

Additional data may be available on the HAO public FTP site.

Utility Tools

TIEGCMrun

TIEGCMrun is a Python tool used to compile and execute TIEGCM in an automated fashion. It can be run interactively on the command line. See QuickStart for example usage.

GCMProcpy

GCMProcpy is a Python tool for post-processing and visualization of TIEGCM output. It can be used interactively on the command line or as an API in a Python script. See the GCMProcpy docs for examples.

Documentation and Support

• User's Guide, Model Description, and Release notes: TIEGCM ReadtheDocs
• TGCM website: http://www.hao.ucar.edu/modeling/tgcm
• Discussion / questions: tgcmgroup@ucar.edu

Citation

If you use TIEGCM in your work, please cite both the software and the accompanying paper. Citation metadata is in CITATION.cff.

• Software (this release): 10.5281/zenodo.20076374
• Paper: Wu, H., Wang, W., Pham, K. H., et al. (2025). The NCAR-TIEGCM Version 3.0. Journal of Geophysical Research: Space Physics. 10.1029/2025JA034219

License

TIEGCM is distributed under the NCAR TIE-GCM Open Source Academic Research License Agreement. The full text is in LICENSE and applies to v2, v3, and subsequent versions.