Using platform magnetometers to resolve dynamics of polar ionospheric currents

Polar ground magnetic disturbances often change by several nT per minute, reflecting large variations in ionospheric currents. Understanding such rapid variations is not only a significant research challenge in space physics, but also important for predicting hazardous induced currents. Ground magnetometer networks like INTERMAGNET and SuperMAG have made it possible to to analyze the ground magnetic disturbance field at a global scale at high time resolution. However, to get a complete picture of the 3-dimensional ionospheric current system, including the coupling to the magnetosphere via field-aligned currents, magnetic field measurements in space are essential. To resolve the large-scale current dynamics at high time resolution, we need a fleet of satellites in space carrying magnetometers, similar to the ground magnetometer networks. Recent progress in the calibration and dissemination of platform magnetometer data, from spacecraft that were not primarily designed for geomagnetic analyses, provide such a dataset. We will discuss and demonstrate how these new datasets can be used to determine the dynamics of the 3D ionospheric current system. We will show how it can help resolve detailed variations in statistical analyses of substorm currents. We will also demonstrate how it can contribute to analyses of the 3D ionospheric currents in regional inversions, using spherical elementary current functions.