pymagglobal

python interface for global geomagnetic field models

• pymagglobal
  • License
  • Citation
  • Documentation
  • Installation
  • Contact
  • References

pymagglobal serves the purpose of replacing some Fortran scripts, which are used in the geomagnetism community to evaluate global field models.
It can be applied to all cubic-spline based geomagnetic field models stored in the same file format as gufm1 or the CALSxk model series. However, care has to be taken that two header lines of the model files are formatted correctly and the list of spline knot point epochs starts only in line 3. The first header line has to contain start and end epoch of the model as the first two numbers, any further information in that line is ignored. The second header line has to start with three integers, which are the maximum spherical harmonic degree, a dummy that actually is not used, and the number of splines.
By default, pymagglobal includes several models. Use

$ pymagglobal --list-models

to get a list of these default models or go to pymagglobal/dat for further information. Using

$ pymagglobal --input <path/to/your_model> ... your.model

you can use pymagglobal to evaluate your own models, if they come in a similar format. <path/to/your_model> specifies the path to your model file and your.model the name of your model. You can download additional models here and use them as above.

Once installed, pymagglobal can be imported and its routines used to access the models from inside your own python code.

License

GNU General Public License, Version 3, 29 June 2007

Copyright (C) 2020 Helmholtz Centre Potsdam GFZ, German Research Centre for Geosciences, Potsdam, Germany

pymagglobal is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

pymagglobal is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.

Citation

TODO

Documentation

From the command line, you can use pymagglobal to get various results from the models. For example,

$ pymagglobal dipole gufm1

will give a plot of the dipole moment time series for the model gufm1. In general, pymagglobal is called as

$  pymagglobal command --options model

where command specifies the quantity you want to get from pymagglobal and model is the respective model. You can use

$ pymagglobal -i <path/to/your_model> command --options your.model

to parse your own model, if it is in a format similar to gufm1. Use

$ pymagglobal --help

to get further information. Each command has its own help, so you may also use

$ pymagglobal dipole --help

to get information on the options for the dipole time series.

When using python you can import the pymagglobal package and access the models directly:

import pymagglobal

Using the function file2splines you can get a spline object, representing the model. For example, to get a spline object for gufm1, use

gufm1_splines = pymagglobal.file2splines(pymagglobal.models['gufm1'])

This object can be evaluated to get the coefficients for a specific epoch

gufm1_1600 = gufm1_splines(1600)

or passed to other routines in pymagglobal. For example, to get the dipole series from above use

import numpy as np

times = np.linspace(1590, 1990, 201)
gufm1_dipoles = pymagglobal.dipole_series(times, gufm1_splines)

Installation

pymagglobal is built and installed using conda.

0. Clone the repository

    $ git clone https://gitext.gfz-potsdam.de/arthus/pymagglobal.git

   In the following <pymagglobal> refers to the path you cloned the pymagglobal repository into.

1. Download and install Miniconda for Python 3 By default, the installation directory <conda> is ~/miniconda3/.
   If you do not allow conda to modify your bash.rc, conda has to be replaced by <conda>/bin/conda. This may cause install.sh to fail.
   You may want to create a fresh environment for pymagglobal. This is done using

   $ conda create --name Your_Environment

   followed by

   $ conda activate Your_Environment

   Careful: With tcshell, you have to use activate.csh.

2. Install conda-build

   $ conda install conda-build

With conda-build installed, you may go to <pymagglobal> and run

$ bash install.sh

which will do the next steps for you. If install.sh fails or you want to do the steps by hand:

3. Build FieldTools
   This step will make the pyfield library available via the local conda channel.

   Navigate to <pymagglobal> and build FieldTools

   $ conda build FieldTools

4. Build pymagglobal
   Navigate to <pymagglobal> and build pymagglobal

   $ conda build ./

5. Install pymagglobal

   $ conda install pymagglobal -c local

   This will make pymagglobal available as a python package, i.e. you can use

   import pymagglobal

   as well as register a shell command in your local environmet, so that you can run

   $ pymagglobal --help

Contact

• Maximilian Schanner
  Helmholtz Centre Potsdam German Research Centre for Geoscienes GFZ
  Section 2.3: Geomagnetism
  Telegrafenberg
  14473 Potsdam, Germany

References

pymagglobal uses numpy, scipy, matplotlib, cartopy and pyfield:

[scipy] Pauli Virtanen, Ralf Gommers, Travis E. Oliphant, Matt Haberland,
Tyler Reddy, David Cournapeau, Evgeni Burovski, Pearu Peterson,
Warren Weckesser, Jonathan Bright, Stéfan J. van der Walt, Matthew Brett,
Joshua Wilson, K. Jarrod Millman, Nikolay Mayorov, Andrew R. J. Nelson,
Eric Jones, Robert Kern, Eric Larson, CJ Carey, İlhan Polat, Yu Feng,
Eric W. Moore, Jake VanderPlas, Denis Laxalde, Josef Perktold, Robert Cimrman,
Ian Henriksen, E.A. Quintero, Charles R Harris, Anne M. Archibald,
Antônio H. Ribeiro, Fabian Pedregosa, Paul van Mulbregt,
and SciPy 1.0 Contributors (2020)
"SciPy 1.0: Fundamental Algorithms for Scientific Computing in Python".
Nature Methods, in press.

[matplotlib] J. D. Hunter (2007)
"Matplotlib: A 2D Graphics Environment",
Computing in Science & Engineering, vol. 9, no. 3, pp. 90-95

[cartopy] Met Office (2015)
"Cartopy: a cartographic python library with a Matplotlib interface"

[pyfield] Matuschek, H. and Mauerberger, S. (2019)
FieldTools - A toolbox for manipulating vector fields on the sphere
GFZ Data Services. 10.5880/fidgeo.2019.033