conjugate_map: A Python package for calculating geomagnetic conjugate points

The Earth’s magnetic field is dominated by the dipole moment, which magnetically connects the northern and southern hemispheres. Because ionospheric and magnetospheric plasmas preferentially move along magnetic field lines, local processes that affect the ionosphere or magnetosphere in one hemisphere can cause changes in the opposite hemisphere. The polar regions are uniquely valuable in geospace science, in part because much of the solar wind’s energy enters the system in polar regions and their magnetospheric, ionospheric, and atmospheric connections are markedly different from the lower latitudes. Geomagnetic conjugates are points in the northern and southern hemispheres linked by Earth’s magnetic field, including both points connected by closed magnetic field lines and points in open-field line regions that are in similar magnetic domains. Conjugate locations are both affected asymmetrically by external factors and have also been shown to alter each other’s environment on the order of minutes, which makes interhemispheric comparisons crucial to understanding the full dynamics of the geospace system. Here, we present conjugate_map, a Python library for flexible geomagnetic coordinate conversions that was designed to facilitate interhemispheric comparisons of geospace events and deployment of polar geospace instruments. As the fifth International Polar Year approaches in 2032–33, this work will help researchers to incorporate interhemispheric geospace investigations into the instrument planning process.