Forecasting Auroral Electrodynamic Parameters Using Global Measurements of Field-Aligned Currents

Abstract:

Forecasting space weather conditions and impacts in the ionosphere and thermosphere requires accurate specification of auroral energy input and auroral electrodynamic properties globally and continuously. Field-aligned currents are essential elements of magnetosphere—ionosphere coupling processes at high latitudes. When combined with electrical conductances, global measurements of field-aligned currents can be used to estimate electric fields, currents, and Joule heating. In the past, the challenge has been to specify ionospheric conductances with the spatial coverage and temporal cadence necessary for accurate and complete auroral specification. One approach to addressing this challenge is to derive the conductances from measurements of field-aligned currents, now available globally and continuously from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). The relation between field-aligned currents and conductances is derived experimentally by combining AMPERE observations with electron density measurements from the Poker Flat Incoherent Scatter Radar (PFISR). The data were used to establish statistical relationships between field-aligned currents and conductances. The PFISR data can also be used to derive relations between field-aligned currents and auroral energy flux. With the assumption that these relationships apply to all geographic locations, auroral conductances can be determined with the same spatial resolution and temporal cadence as the field-aligned currents. The electric fields and currents derived from the field-aligned currents and conductances compare well with those obtained from other ground-based and space-based observing platforms. For space weather forecasting, these results suggest that for specification of auroral properties, it is sufficient to accurately determine the field-aligned currents resulting from solar wind drivers. All other electrodynamic parameters derive from the field-aligned currents alone.