An Analysis of Two-Dimensional Field Line Resonance Flows, Field-Aligned Currents and Periodic Auroral Arcs

Field line resonances (FLRs) are standing shear Alfven waves along Earth's magnetic field lines. They play an important role in solar wind-magnetosphere-ionosphere coupling and the generation of some types of auroral forms. The Super Dual Auroral Radar Network (SuperDARN) is an excellent tool for studying FLRs as it provides two-dimensional ionospheric plasma convection over large spatial areas with a temporal resolution of 1 minute. Using SuperDARN ionospheric convection maps, the two-dimensional plasma flows corresponding to a specific frequency FLR are determined. The FLR wave plasma flows exhibit significant vorticity and are used to estimate the field-aligned currents generated by the FLR. The estimated FLR field-aligned currents oscillate between upward going and downward going at the periodicity of the FLR wave and follow the phase propagation of the wave. Using typical values for height-integrated Pedersen conductivity, the FLR field-aligned currents are estimated to be on the order of 1 mA/m2. Comparison with simultaneous REGO and THEMIS all-sky images shows good correspondence between periodic discrete auroral arcs and the SuperDARN FLRs. The direction of the peak FLR flows follow the East-West line of the auroral arc with the peak intensity of the arc occurring just equatorward of the maximum in the FLR flow amplitude. Simultaneous conjunctions with the SWARM spacecraft show significant SWARM field-aligned currents conjugate to the location of the SuperDARN FLRs. The purpose of this work is to provide a new understanding of FLRs and the role they play in the generation of some auroral forms.