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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 34, issue 9
Ann. Geophys., 34, 831–843, 2016
https://doi.org/10.5194/angeo-34-831-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 34, 831–843, 2016
https://doi.org/10.5194/angeo-34-831-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 21 Sep 2016

Regular paper | 21 Sep 2016

Determination of errors in derived magnetic field directions in geosynchronous orbit: results from a statistical approach

Yue Chen, Gregory Cunningham, and Michael Henderson Yue Chen et al.
  • Los Alamos National Laboratory, Los Alamos, New Mexico, USA

Abstract. This study aims to statistically estimate the errors in local magnetic field directions that are derived from electron directional distributions measured by Los Alamos National Laboratory geosynchronous (LANL GEO) satellites. First, by comparing derived and measured magnetic field directions along the GEO orbit to those calculated from three selected empirical global magnetic field models (including a static Olson and Pfitzer 1977 quiet magnetic field model, a simple dynamic Tsyganenko 1989 model, and a sophisticated dynamic Tsyganenko 2001 storm model), it is shown that the errors in both derived and modeled directions are at least comparable. Second, using a newly developed proxy method as well as comparing results from empirical models, we are able to provide for the first time circumstantial evidence showing that derived magnetic field directions should statistically match the real magnetic directions better, with averaged errors  < ∼ 2°, than those from the three empirical models with averaged errors  > ∼ 5°. In addition, our results suggest that the errors in derived magnetic field directions do not depend much on magnetospheric activity, in contrast to the empirical field models. Finally, as applications of the above conclusions, we show examples of electron pitch angle distributions observed by LANL GEO and also take the derived magnetic field directions as the real ones so as to test the performance of empirical field models along the GEO orbits, with results suggesting dependence on solar cycles as well as satellite locations. This study demonstrates the validity and value of the method that infers local magnetic field directions from particle spin-resolved distributions.

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This study statistically quantifies the errors in local magnetic field directions that are derived from electron directional distributions measured by Los Alamos National Laboratory geosynchronous (LANL GEO) satellites. We demonstrate for the first time that derived magnetic field directions in GEO orbit should statistically match the real magnetic directions ~2 times better than those from a list of empirical models and have no significant dependence on magnetospheric activities.
This study statistically quantifies the errors in local magnetic field directions that are...
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