The general understanding of the global electrodynamics of an auroral ARC has been established for many years, however the mesoand micro- scale details of the geometry of the current systems and…

This is a $3,321,138.26 grant awarded by a civilian federal agency to The University of Iowa to conduct the Aurora Current and Electrodynamics Structure (ACES II) sounding rocket experiment. The objective is to better understand the geometry and electrodynamics of auroral arcs by taking detailed measurements at key altitudes using two instrumented sounding rockets. This will provide empirical data to constrain theoretical models of auroral processes. The contract has no set-aside designation and is a grant for research with a completion date of April 30, 2025. The University of Iowa is the prime awardee and will be leveraging its expertise in space physics and plasma research to execute this investigation.

The general understanding of the global electrodynamics of an auroral ARC has been established for many years, however the mesoand micro- scale details of the geometry of the current systems and electrodynamics within the ARC structure is typically theoretically modeled and lacks broader experimental confirmation and empirical data to constrain the models. Single point measurement of a large-scale system or the spatial/temporal limitations of satellite passes can only provide a glimpse of a piece of the auroral electrodynamics. Even modern multi-spacecraft missions and near satellite conjunctions cannot provide sufficient resolution of these geometries due to the "randomness" of the conjunction in both space and time relative to each other and the ARC system. Furthermore, no active project provides measurements at the important altitudes (~120KM) of the aurora current closure. To investigate the geometry and electrodynamics of a complete auroral ARC system requires a controlled placement of the appropriate instrumentation in the important regions within an ARC structure. We propose here two appropriately instrumented sounding rocket payloads, with specific trajectories to place them simultaneously at key altitudes and transits across the auroral ARC structure, to provide detailed measurements of the key plasma parameters. These data will provide constraints for and confirmation of the models and theories related to auroral ARC structure and electrodynamics. The science objective for the proposed investigation is to determine the distribution of the ionospheric currents and the associated energy dissipation in a stable ARC. To address the structure of an auroral ARC, appropriate measurements must be made at points above the ARC and within the current closure region. The aces II experiment will utilize two suitably instrumented rockets at two key altitudes within the ARC. One payload will be above the ionospheric f peak to measure the imposed fields and energy input and output across the auroral ARC. The second payload will be at a lower altitude slicing through the classic current closure region (~120KM). Both payloads will be in fight simultaneously to minimize temporal variation between the measurements. Both payloads will be instrumented to measure DC electric and magnetic fields, supra-thermal to energetic electrons and ION distributions, cold plasma density and temperature. In addition, ground based observations will be crucial to support the launch determination as well as the data analysis. The aces II mission will provide unprecedented simultaneous measurements within a stable auroral ARC. When utilized in context of auroral electrodynamics models, these measurements will constrain the numerous model parameters and allow a complete analysis of the physical processes and electrodynamics within an auroral ARC. This mission directly address some of the questions that are key to understanding the near earth plasma environment and in particular ionospheric-magnetospheric coupling as well as ionospheric-thermospheric coupling. These questions are a priority science focus from the heliophysics roadmap.