Low Energy Neutral Atoms and Kappa Ion Distributions in the Heliosheath

Thursday, 18 December 2014: 2:25 PM
Stephen Fuselier1, Frederic Allegrini1, Maciej Bzowski2, Maher A Dayeh1, Mihir Indrajit Desai3, Herbert O Funsten4, Andre Galli5, David Heirtzler6, Paul H Janzen7, Marzena A. Kubiak2, Harald Kucharek8, William S Lewis3, George Livadiotis3, David J McComas1, Eberhard Moebius8, Steven M Petrinec9, Marty Scott Quinn10, Nathan Schwadron6, Justyna M Sokol2 and Karlheinz J Trattner11, (1)Southwest Research Institute San Antonio, San Antonio, TX, United States, (2)Space Research Center Polish Academy of Sciences, Warsaw, Poland, (3)Southwest Research Institute, San Antonio, TX, United States, (4)Los Alamos Natl Laboratory, Los Alamos, NM, United States, (5)University of Bern, Bern, Switzerland, (6)University of New Hampshire, Durham, NH, United States, (7)University of Montana, Missoula, MT, United States, (8)Univ New Hampshire, Durham, NH, United States, (9)Lockheed Martin Space Systems, Cupertino, CA, United States, (10)University of New Hampshire Main Campus, Durham, United States, (11)Laboratory for Atmospheric and Space Physics, Boulder, CO, United States
In the heliosheath beyond the termination shock, low-energy (<0.5 keV) neutral atoms are created by charge exchange of ions with interstellar neutrals. Detecting these neutrals from Earth orbit is challenging because their flux is reduced substantially by ionization losses as they propagate from about 100 AU to 1 AU and because the measured flux competes with a variety of other signals and backgrounds. Using observations from IBEX-Lo and -Hi from two opposing vantage points in Earth orbit, a lower energy limit of about 0.1 keV on measurements of ENAs from the heliosphere and the characteristics of the energy spectrum from about 0.1 to 6 keV are established in two directions in the sky. The ion distribution that produces these neutrals is very kappa-like over 2 decades in energy, based on the ENA observations. When combined with in situ Voyager ion measurements, this kappa-like behavior extends over 5 decades in energy. This presentation focuses on the origins of the kappa-like ion distribution, particularly at lower energies, and investigates the implications for the ion-neutral interactions in the heliosheath.