APEX

Fortran code to convert between geographic and magnetic quasi-dipole, magnetic apex, and modified magnetic apex coordinate systems based on Van Zandt et al. (1972) and Richmond [1995]. The geomagnetic main field is the International Geomagnetic Reference Field (IGRF) Version 13. The test program includes:

• Magnetic apex parameters for a given location
• Base vectors for scaling electric field and ion velocity components
• Magnetic footpoints in both hemispheres for a given geographic point
• Conversion between quasi-dipole and geographic coordinates
• Subsolar point, solar zenith angle, magnetic local time

Date and time, positions (geographic longitude, latitude, altitude)

• Magnetic apex parameters for a given location
• Base vectors for scaling electric field and ion velocity components
• Magnetic footpoints in both hemispheres for a given geographic point
• Conversion between quasi-dipole and geographic coordinates
• Subsolar point, solar zenith angle, magnetic local time

05/2025:

• Update to add the ability to read the IGRF coffecients from the file provided by NGDC at https://www.ngdc.noaa.gov/IAGA/vmod/coeffs/igrf14coeffs.txt. This will be come the default behavior with the next update of IGRF.
• Includes IGRF-14 coefficients published in late 2024