Mismatch between T89 results for IDL and Python

spedas / pyspedas

Python-based Space Physics Environment Data Analysis Software

https://pyspedas.readthedocs.io/

MIT License

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Mismatch between T89 results for IDL and Python #614

Closed jameswilburlewis closed 1 year ago

jameswilburlewis commented 1 year ago

I compared the results of applying the IDL and Python T89 field models to the THEMIS-A ephemeris for 2007-03-23. The results differed by up to +/- 2000 nT around perigee. The difference is still there when using the igrf_only keywords.

jameswilburlewis commented 1 year ago

The pyspedas t89 wrapper was using the geopack.dip() (simple dipole) as the internal model, rather than geopack.igrf_gsm() (IGRF model). With geopack.igrf_gsm(), the differences are now down to +/- .25 nT near perigee.