Heliospheric neutral atom spectra between 0.01 and 6keV from IBEX

S. A. Fuselier, F. Allegrini, M. Bzowski, H. O. Funsten, A. G. Ghielmetti, G. Gloeckler, D. Heirtzler, P. Janzen, M. Kubiak, H. Kucharek, D. J. McComas, E. Möbius, T. E. Moore, S. M. Petrinec, M. Quinn, D. Reisenfeld, L. A. Saul, J. A. Scheer, N. Schwadron, K. J. TrattnerR. Vanderspek, P. Wurz

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Since 2008 December, the Interstellar Boundary Explorer (IBEX) has been making detailed observations of neutrals from the boundaries of the heliosphere using two neutral atom cameras with overlapping energy ranges. The unexpected, yet defining feature discovered by IBEX is a Ribbon that extends over the energy range from about 0.2 to 6keV. This Ribbon is superposed on a more uniform, globally distributed heliospheric neutral population. With some important exceptions, the focus of early IBEX studies has been on neutral atoms with energies greater than 0.5keV. With nearly three years of science observations, enough low-energy neutral atom measurements have been accumulated to extend IBEX observations to energies less than 0.5keV. Using the energy overlap of the sensors to identify and remove backgrounds, energy spectra over the entire IBEX energy range are produced. However, contributions by interstellar neutrals to the energy spectrum below 0.2keV may not be completely removed. Compared with spectra at higher energies, neutral atom spectra at lower energies do not vary much from location to location in the sky, including in the direction of the IBEX Ribbon. Neutral fluxes are used to show that low energy ions contribute approximately the same thermal pressure as higher energy ions in the heliosheath. However, contributions to the dynamic pressure are very high unless there is, for example, turbulence in the heliosheath with fluctuations of the order of 50-100kms-1.

Original languageEnglish (US)
Article number14
JournalAstrophysical Journal
Issue number1
StatePublished - Jul 20 2012
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • ISM: molecules
  • Sun: heliosphere
  • interplanetary medium
  • plasmas
  • solar wind


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