Dipole - calculations involving dipole model of Earth's magnetic field

Python code to calculate

• dipole magnetic field
• dipole tilt angle
• centered dipole coordinates and vector components
• magnetic local time
• dipole pole locations
• magnetic flux poleward of some boundary
• apex base vectors for a dipole magnetic field

The calculations use time-dependendent IGRF coefficients (see https://www.ngdc.noaa.gov/IAGA/vmod/igrf.html for details and https://doi.org/10.1186/s40623-020-01163-9 for even more details) accessed through the ppigrf Python module (https://github.com/klaundal/ppigrf).

For a definition of centered dipole coordinates, see Section 3.1 in https://doi.org/10.1007/s11214-016-0275-y

The code is vectorized, so all calculations should be pretty fast.

Examples

Here is an example calculation of dipole tilt angle. In this example, a Dipole object is initialized for epoch 2022.5, and dipole tilt angle is calculated for two different times

import dipole
from datetime import datetime

dates = [datetime(2022, 7, 13, 10, 0, 0), datetime(2022, 7, 13, 22, 0, 0)]
tilts = dipole.Dipole(2022.5).tilt(dates)

Here is an example converting northward-pointing unit vectors from geocentric to centered dipole coordinates. This example also illustrates how numpy broadcasting rules are used for input with different shapes

import dipole
import numpy as np

lat = 70
lon = np.r_[0:360:15]
north = 1
east = 0

d = dipole.Dipole(2010.) # IGRF epoch 2010.
cdlat, cdlon, cd_east, cd_north = d.geo2mag(lat, lon, Ae = east, An = north)

Contact

If you find errors, please let me know!

You don't need permission to copy or use this code.

karl.laundal at uib.no