First ENA observations at Mars: ENA emissions from the martian upper atmosphere

Y. Futaana*, S. Barabash, A. Grigoriev, M. Holmström, E. Kallio, P. C. Brandt, H. Gunell, K. Brinkfeldt, R. Lundin, H. Andersson, M. Yamauchi, S. McKenna-Lawler, J. D. Winningham, R. A. Frahm, J. R. Sharber, J. R. Scherrer, A. J. Coates, D. R. Linder, D. O. Kataria, T. SälesP. Riihelä, W. Schmidt, H. Koskinen, J. Kozyra, J. Luhmann, E. Roelof, D. Williams, S. Livi, C. C. Curtis, K. C. Hsieh, B. R. Sandel, M. Grande, M. Carter, J. A. Sauvaud, A. Fedorov, J. J. Thocaven, S. Orsini, R. Cerulli-Irelli, M. Maggi, P. Wurz, P. Bochsler, A. Galli, N. Krupp, J. Woch, M. Fränz, K. Asamura, C. Dierker

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

47 Citations (SciVal)

Abstract

The neutral particle detector (NPD) on board Mars Express has observed energetic neutral atoms (ENAs) from a broad region on the dayside of the martian upper atmosphere. We show one such example for which the observation was conducted at an altitude of 570 km, just above the induced magnetosphere boundary (IMB). The time of flight spectra of these ENAs show that they had energies of 0.2-2 keV/amu, with an average energy of ∼1.1 keV/amu. Both the spatial distribution and the energy of these ENAs are consistent with the backscattered ENAs, produced by an ENA albedo process. This is the first observation of backscattered ENAs from the martian upper atmosphere. The origin of these ENAs is considered to be the solar wind ENAs that are scattered back by collision processes in the martian upper atmosphere. The particle flux and energy flux of the backscattered ENAs are 0.9 - 1.3 × 107   cm-2 s-1 and ∼ 9.5 × 109   eV cm-2 s-1, respectively.

Original languageEnglish
Pages (from-to)424-430
Number of pages7
JournalIcarus
Volume182
Issue number2
DOIs
Publication statusPublished - Jun 2006

Keywords

  • atmosphere
  • Atmospheres
  • dynamics
  • Ionospheres
  • Mars
  • Solar wind
  • structure

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