Observations of neutral atoms from the solar wind Michael R. Collier (1), Thomas E. Moore (1), Keith W. Ogilvie (1), Dennis Chornay (1,2), J.W. Keller (1), S. Boardsen (1,3), James Burch (4), B. El Marji (1,2), M.-C. Fok (1), S.A. Fuselier (5), A.G. Ghielmetti (5), B.L. Giles (1), D.C. Hamilton (6), B.L. Peko (7), J.M. Quinn (8), E.C. Roelof (9), T.M. Stephen (7), G.R. Wilson (10), and P. Wurz (11) (1) NASA Goddard Space Flight Center, Greenbelt, Maryland (2) Department of Astronomy, University of Maryland, College Park, Maryland (3) Raytheon ITSS Corporation, Lanham, Maryland (4) Southwest Research Institute, San Antonio, Texas (5) Lockheed Martin Advanced Technology Center, Palo Alto, California (6) Department of Physics, University of Maryland, College Park, Maryland (7) Department of Physics and Astronomy, University of Denver, Denver, Colorado (8) Space Science Center, University of New Hampshire, Durham, New Hampshire (9) Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland (10) Mission Research Corporation, Nashua, New Hampshire (11) Physics Institute, University of Bern, Bern, Switzerland We report observations of neutral atoms in the solar wind in the Earth's vicinity with the low-energy neutral atom (LENA) imager on the Imager for Magnetopause-to- Aurora Global Exploration (IMAGE) spacecraft. This instrument was designed to be capable of looking at and in the direction of the Sun. Enhancements in the hydrogen count rate in the solar direction are not correlated with either solar ultraviolet emission or suprathermal ions and are deduced to be due to neutral particles from the solar wind. LENA observes these particles from the direction closest to that of the Sun even when the Sun is not directly within LENA's 90 degree field of view. Simulatiuons show that these neutrals are the result of solar wind ions charge exchanging with exospheric neutral hydrogen atoms in the postshock flow of the solar wind in the magnetosheath. Their energy is inferred to exceed 300 eV, consistent with solar wind energies, based on the simulation results and on the observation of oxygen ions, sputtered from the conversion surface in the time-of-flight spectra. In addition, the sputtered oxygen abundance tracks the solar wind speed, even when IMAGE is deep inside the magnetosphere. These results show that low-energy neutral atom imaging provides the capability to directly monitor the solar wind flow in the magnetosheath from inside the magnetosphere because there is a continuous and significant flux of neutral atoms originating from the solar wind that permeates the magnetosphere. _______________ J. Geophys. Res., 106, 24893-24906, November, 2001