A review of Birkeland current research using AMPERE

We review research into the Birkeland currents (also known as field-aligned currents) that has been conducted using the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). We open with a short review of the history of research into the Birkeland current systems, before describing the conception of AMPERE and its roots in Iridium telecommunications satellite engineering telemetry data. We describe the difference between Iridium engineering telemetry data and AMPERE data, and review the work that has been done using both datasets. We review research into Regions 1 and 2 Birkeland current during geomagnetic storms and consequently the ways in which the currents are driven by the solar wind, before moving onto the substorm current wedge and discussing the present controversy over this phenomenon in AMPERE data. Ways in which AMPERE data can be used to examine ionospheric conductivity are detailed alongside ways in which AMPERE has contributed to empirical models of the coupled solar wind-magnetosphere- ionosphere system. Finally, we look to the future and speculate on the manner in which AMPERE may yet unlock the secrets of the magnetosphere.