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Ann. Geophys., 26, 1641-1652, 2008
www.ann-geophys.net/26/1641/2008/
© European Geosciences Union 2008
Iterative inversion of global magnetospheric ion distributions using energetic neutral atom (ENA) images recorded by the NUADU/TC2 instrument
L. Lu1, S. McKenna-Lawlor2, S. Barabash3, K. Kudela4, J. Balaz2,4, I. Strharsky2,4, Z. X. Liu1, C. Shen1, J. B. Cao1, P. C. Brandt5, C. L. Tang6, and I. Dandouras7
1Centre for Space Science and Applied Research of the Chinese Academy of Sciences, Beijing, China
2Space Technology Ireland, National University of Ireland, Maynooth, Co. Kildare, Ireland
3Swedish Institute of Space Physics, Kiruna, Sweden
4Institute of Experimental Physics, Kosice, Slovakia
5The Johns Hopkins University Applied Physics Laboratory, Laurel MD, USA
6School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China
7Centre d'Etude Spatiale des Rayonnements, Toulouse, France
Abstract. A method has been developed for extracting magnetospheric
ion distributions from Energetic Neutral Atom (ENA) measurements made by the
NUADU instrument on the TC-2 spacecraft. Based on a constrained linear
inversion, this iterative technique is suitable for use in the case of an
ENA image measurement, featuring a sharply peaked spatial distribution. The
method allows for magnetospheric ion distributions to be extracted from a
low-count ENA image recorded over a short integration time (5 min). The
technique is demonstrated through its application to a set of representative
ENA images recorded in energy Channel~2 (hydrogen: 50–81 keV, oxygen:
138–185 keV) of the NUADU instrument during a geomagnetic storm. It is
demonstrated that this inversion method provides a useful tool for
extracting ion distribution information from ENA data that are characterized
by high temporal and spatial resolution. The recovered ENA images obtained
from inverted ion fluxes match most effectively the measurements made at maximum
ENA intensity.
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