Authors: Pete Riley, J.A. Linker, R. Lionello, Z. Mikic; D. Odstrcil; M.
A. Hidalgo; Q. Hu; R.P. Lepping; B.J. Lynch; A. Rees
Affiliation: Science Applications International Corporation, San Diego. California;
National Oceanic and Atmospheric Administration, Space Environment Center; Departamento
de Fisica, Universidad de Alcala, Madrid, Spain; Thayer School of Engineering,
Dartmouth College; NASA Goddard Space Flight Center, Laboratory for Extraterrestrial
Physics; University of Michigan, Ann Arbor; The Blackett Laboratory, Imperial
College London, UK
Flux rope fitting (FRF) techniques have been shown to be an invaluable tool for extracting information about the properties of a sub-class of CMEs in the solar wind. However, it has proven difficult to assess their accuracy since the underlying global structure of the CME cannot be independently determined. In contrast, large-scale MHD simulations of CME evolution can provide both a global view as well as localized timeseries at specific points in space. In this study we apply 5 different fitting techniques to 2 hypothetical timeseries derived from MHD simulation results. Independent teams performed the analysis of the events in "blind tests", for which no information, other than the timeseries, was provided. From the results, we infer the following: (1) Accuracy decreases markedly with increasingly glancing encounters; (2) Correct identification of the boundaries of the flux rope can be a significant limiter; and (3) Results from techniques that infer global morphology must be viewed with caution. In spite of these limitations, FRF techniques remain a useful tool for describing in situ observations of flux rope CMEs.