Geopack-2008 — GEOPACK-2008 geomagnetic field model for Python

Geopack-2008 (imported as geopack) is a high-performance, self-contained, zero-dependency Python package for the GEOPACK-2008 geomagnetic field model: the International Geomagnetic Reference Field (IGRF), the dipole field, the Tsyganenko (1989) external field model (T89), the Shue et al. (1998) and Tsyganenko (1996) magnetopause models, the Sun position computation, and the standard solar-terrestrial coordinate transforms (GEO, GSW, GSE, SM, MAG, GEI, GSM).

It is a Python binding over a C# port of GEOPACK-2008 compiled ahead-of-time with NativeAOT into a shared library (geopack.dylib / geopack.so / geopack.dll), loaded through ctypes from the Python standard library. No .NET runtime is required at runtime, and there are no Python dependencies (no NumPy/SciPy).

• High performance: native compiled code with SIMD vectorization and other optimized mathematical operations
• Double precision: accuracy matches the original Fortran code to 12–13 decimal digits
• Standard library only — no third-party runtime dependencies
• Thread-safe immutable computation contexts
• Platform wheels for Linux (x64/arm64), Windows (x64/arm64) and macOS (arm64)

Install

pip install geopack-2008

Pre-built wheels are published to PyPI for Linux (x64/arm64, manylinux), Windows (x64/arm64) and macOS (arm64) — no .NET SDK or C toolchain required.

To build the wheel from source (e.g. for another platform or during development), see BUILDING.md.

Usage

import geopack

ctx = geopack.recalc(1997, 12, 16, 21, 0, 0, vx=-304, vy=13.78, vz=4)
b = ctx.igrf_gsw(1, 1, 1)     # (bx, by, bz) nT in GSW
r = ctx.gsw_to_geo(1, 1, 1)   # (x, y, z) Earth radii in GEO
ctx.close()

# A datetime works too, and contexts are context managers:
with geopack.recalc(datetime(1997, 12, 16, 21, 0), vx=-304, vy=13.78, vz=4) as ctx:
    b = ctx.igrf_gsw(1, 1, 1)

s = geopack.sun(1997, 12, 16, 21, 0, 0)   # (gst, slong, srasn, sdec), radians

mp = geopack.shu_mgnp(xn_pd=2.0, vel=400.0, bz_imf=0.0, x=10, y=0, z=0)
print(mp.boundary, mp.dist, mp.position)  # Vector3, float, MagnetopausePosition

# Tsyganenko (1989) external field — input GSW, output GSM (nT):
b = geopack.t89(iopt=3, psi=ctx.psi, x=-6.6, y=0, z=0)
b = ctx.t89(iopt=3, x=-6.6, y=0, z=0)     # psi defaults to ctx.psi

A runnable example with all of the above (sun position, IGRF/dipole fields, coordinate transforms, magnetopause models) is in python/example.py:

python3 python/example.py

Implemented models and coordinate systems

Supported coordinate systems (see CoordinateSystem): GEO (geographic), GSW (geocentric solar wind), GSE (geocentric solar ecliptic), SM (solar magnetic), MAG (geomagnetic), GEI (geocentric solar equatorial inertial) and GSM (geocentric solar magnetospheric).

API

All coordinates are in Earth radii; magnetic fields are in nT; angles are in radians; solar wind velocity is in km/s.

• recalc(date_or_year, month=None, day=None, hour=0, minute=0, second=0, vx=-400, vy=0, vz=0) -> Context
• Context methods:
  • fields: igrf_gsw(x,y,z), dip(x,y,z), igrf_geo(r,theta,phi), t89(iopt,x,y,z, psi=None), property psi (dipole tilt, radians)
  • transforms: gsw_to_gse, gse_to_gsw, geo_to_mag, mag_to_geo, gei_to_geo, geo_to_gei, mag_to_sm, sm_to_mag, sm_to_gsw, gsw_to_sm, geo_to_gsw, gsw_to_geo — each (x,y,z) -> (x,y,z)
  • lifecycle: close(), context manager
• sun(...) -> Sun(gst, slong, srasn, sdec) — no context needed
• shu_mgnp(xn_pd, vel, bz_imf, x, y, z) and t96_mgnp(xn_pd, vel, x, y, z) return MagnetopauseResult(boundary, dist, position) — no context needed
• t89(iopt, psi, x, y, z, parmod=None) -> Vector3 — Tsyganenko (1989) external field, input GSW, output GSM (nT); parmod is a dummy accepted for parity with the .NET IT89.Calculate contract (unused) — no context needed

GEOPACK_LIBRARY environment variable points the loader at a specific library path if the packaged one is not present.

How to Cite

If you use this software in your research, please cite it — see the How to Cite section of the main repository README (APA and BibTeX entries with a Zenodo DOI).

References

The implementation is based on the GEOPACK-2008 library and the following scientific works:

1. Tsyganenko, N. A. (1989). A magnetospheric magnetic field model with a warped tail current sheet. Planetary and Space Science, 37(1), 5–20. https://doi.org/10.1016/0032-0633(89)90066-4

2. Tsyganenko, N. A. (1996). Effects of the solar wind conditions on the global magnetospheric configuration as deduced from data-based field models. ESA SP-389, 181–185.

3. Shue, J.-H., et al. (1998). Magnetopause location under extreme solar wind conditions. Journal of Geophysical Research, 103(A8), 17691–17700. https://doi.org/10.1029/98JA01103

4. Hapgood, M. A. (1992). Space physics coordinate transformations: A user guide. Planetary and Space Science, 40(5), 711–717. https://doi.org/10.1016/0032-0633(92)90012-D

5. Tsyganenko, N. A. (2002). A model of the near magnetosphere with a dawn-dusk asymmetry 1. Mathematical structure. Journal of Geophysical Research, 107(A8). https://doi.org/10.1029/2001JA000219

6. Tsyganenko, N. A., & Sitnov, M. I. (2005). Modeling the dynamics of the inner magnetosphere during strong geomagnetic storms. Journal of Geophysical Research: Space Physics, 110(A3), A03208. https://doi.org/10.1029/2004JA010798