APEX Fortran Code
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 . 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
**Download from https://github.com/NCAR/apex_fortran.**
***In case you need the updated coefficient file with IGRF13 in an older format please download here.
References for apex coordinate systems:
- Emmert, J.T., Richmond, A.D., & Drob, D.P. (2010). A computationally compact representation of Magnetic-Apex and Quasi-Dipole coordinates with smooth base vectors. Journal of Geophysical Research, 115, A08322. https://doi.org/10.1029/2010JA015326
- Laundal, K.M. & Richmond, A.D. (2017). Magnetic coordinate systems. Space Science Reviews, 206, 27-59. https://doi.org/10.1007/s11214-016-0275-y
- Richmond, A.D. (1995). Ionospheric electrodynamics using Magnetic Apex Coordinates. Journal of Geomagnetism and Geoelectricity, 47, 191-212. https://doi.org/10.5636/jgg.47.191
- Thébault, E., Finlay, C.C., Beggan, C.D. et al. (2015). International Geomagnetic Reference Field: the 12th generation. Earth, Planets and Space 67, 79. https://doi.org/10.1186/s40623-015-0228-9
VanZandt, T.E., Clark, W.L.,and Warnock, J.M. (1972). Magnetic Apex Coordinates: A magnetic coordinate system for the ionospheric F2 layer, Journal of Geophysical Research, 77, 2406-2411.
Other resources for apex code: