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Cluster Curlometry Limitations in the Ring Current Region
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  • Timothy B Keebler,
  • Michael Liemohn,
  • Timothy B Keebler,
  • Natalia Ganushkina
Timothy B Keebler
University of Michigan

Corresponding Author:[email protected]

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Michael Liemohn
University of Michigan, University of Michigan
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Timothy B Keebler
University of Michigan

Corresponding Author:[email protected]

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Natalia Ganushkina
University of Michigan,Finnish Meteorological Institute
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Abstract

During its ongoing mission, the Cluster II constellation has provided the first small-scale multipoint measurements of the space environment, and dramatically advanced scientific understanding in numerous regimes. One such region is the Earth’s inner magnetospheric ring current, which could now be computed using the curl of the magnetic field over a spacecraft tetrahedron instead of via plasma moments. While this produced the first 3D current estimates, it also produced different results from prior ring current studies with differing magnitudes and correlations with storm indices/local times. In this analysis, we revisit Cluster ring current data via curlometry, and conduct additional quantitative sensitivity simulations using actual spacecraft position data. During the orbits that observed ring current structure, tetrahedron shape and linearity assumptions can create large errors up to 100% of physical current magnitude in curlometer output that contradict accepted estimated quality parameters. These false currents are directly related to the structure of the current environment, and cannot be distinguished from the actual currents without additional limiting assumptions. The trustworthiness of curlometer output in the ring current is therefore dependent on the linearity of the magnetic structure relative to the tetrahedron orientation, which requires additional characterization. The Cluster curlometer output in the ring current is then explored in light of these new uncertainties, with the computed current magnitude and direction both potentially impacted by the production of false currents.