create new source for Bfield based on model
Masafumi and Terry have both written codes for calculating model B-field data based on the JRM model. It's not clear if these versions are up-to-date, and it would be nice to create a source for the data which is known to be up-to-date. Ali pointed me to https://github.com/marissav06/con2020/tree/main/MATLAB which is a matlab code which models the external field, and there is another which models the internal field, linked at https://lasp.colorado.edu/mop/missions/juno/community-code/. We want "order 13", and to calculate both internal and external bfield mag. We want to look at the data, model if data is not available, or model. We want to look at just the internal or with both internal and external summed. We may also want to look at components individually in the future.