Iterative inversion of global magnetospheric information from energy neutral atom (ENA) images recorded by the TC-2/NUADU instrument

Abstract

A method is presented for retrieving the magnetospheric ion distribution from Energetic Neutral Atom (ENA) measurements made by the NUADU instrument on the TC-2 spacecraft. Based on the already well-established method of constrained linear inversion, an iterance technique suitable for the low count ENA measurements has been developed which is tolerant of the noise background. By the iterance technique, it is possible for the first time to simultaneously retrieve the magnetospheric ion distribution and the exospheric neutral density, and further to recover global ENA emissions in three dimensions. The technique is applied to a representative ENA image recorded in energy channel 2 (protons: 50-81 keV) of the NUADU instrument during a major geomagnetic storm and it is, thereby, shown that the retrieval method developed provides a useful tool for extracting ion distribution information from ENA data.Energetic Neutral Atom (ENA), ring current, magnetospheric ions, exospheric neutral density

Energetic Neutral Atom (ENA) Imaging Simulation of the Distant Planetary Magnetosphere and ENA Emission Discussion of the Solar Wind

“…where the collision cross-section of a hydrogen atom σ pH ≈ 10 −15 -10 −16 cm 2 and the density of a hydrogen atom n H ≈ 1-10 cm −3 [28]. Ignore the helium density n He for IBEX-Hi measurements with an ENA differential flux of 10 1 -10 2 cm −2 sr −1 s −1 keV −1 and an ENA integral length of SWIF L ≈ 10 4 -10 5 km.…”

Near-Approach Imaging Simulation of Low-Altitude ENA Emissions by a LEO Satellite

“…Based on TC-2 /NUADU's ENA measurements on November 7, 2004, and inversion of ion flux distribution, a set of 3-D maps of ENA emission source in different magnetic shells was derived (Lu et al, 2008b). The maps reveal that the ENA emission source is located in the low altitude polar region.…”