The Interstellar Boundary Explorer has been directly observing neutral atoms from the local interstellar medium for the last six years (2009)(2010)(2011)(2012)(2013)(2014). This paper ties together the 13 studies in this special issue of the Astrophysical Journal Supplement, which 30 ConfidentialPage 2 6/12/2015 collectively describe the IBEX interstellar neutral results from this epoch and provide a 31 number of other relevant theoretical and observational results. Interstellar neutrals 32 interact with each other and with the ionized portion of the interstellar population in the 33 "pristine" interstellar medium ahead of the heliosphere. Then, in the heliosphere's close 34 vicinity, the interstellar medium begins to interact with escaping heliospheric neutrals. In 35 this study we compare the results from two major analysis approaches led by IBEX groups in New Hampshire and Warsaw. We also directly address the question of the distance upstream to the pristine interstellar medium and adjust both sets of results to a common distance of ~1000 AU. The two analysis approaches are quite different, but yield fully consistent measurements of the interstellar He flow properties, further validating our findings. While detailed error bars are given for both approaches, we recommend that for most purposes, the community use "working values" of ~25.5 km s -1 , ~75.5° ecliptic inflow longitude, ~-5.1° ecliptic inflow latitude, and ~7500 K temperature at ~1000 AU upstream. Finally, we briefly address future opportunities for even better interstellar neutral observations to be provided by the Interstellar Mapping and Acceleration Probe (IMAP) mission, which was recommended as the next major Heliophysics mission by the NRC's 2013 Decadal Survey.

Heliospheric energetic neutral atoms (ENAs) that will be measured by the Interstellar Boundary Explorer (IBEX) originate from the heliosheath. The heliosheath is formed as a result of the interaction of the solar wind (SW) with the circum-heliospheric interstellar medium (CHISM). The expected fluxes of ENAs are strongly dependent on the nature of this interaction. In turn, the interaction of the solar wind with the local interstellar cloud has a complex and multi-component nature. Detailed theoretical modeling of the interaction between the SW and the local interstellar medium is required to understand the physics of the heliosheath and to predict and explain the heliospheric ENAs. This paper summarizes current state-of-art kinetic-gasdynamic models of the SW/CHISM interaction. We shall restrict our discussion to the kinetic-gasdynamic and kinetic-magnetohydrodynamic (MHD) models developed by the Moscow group. This paper summarizes briefly the main results of the first self-consistent, two-component, kinetic-gasdynamic model by Baranov and Malama (J. Geophys. Res. 98:15157-15163, 1993), presents new results obtained from the 3D kinetic-MHD model by Izmodenov et al. (Astron. Astrophys. 437:L35-L38, 2005a), describes the basic formulation and results of the model by Malama et al. (Astron. Astrophys. 445:693-701, 2006) as well as reports current developments in the model. This self-consistent model considers pickup protons as a separate non-equilibrium component. Then we discuss a stochastic acceleration model for pickup protons in the supersonic solar wind and in the heliosheath. We also present the expected heliospheric ENA fluxes obtained in the framework of the models.

The high‐resolution echelle mode of the Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile Evolution mission has been designed to measure D and H Lyman α emissions from the Martian atmosphere to obtain key information about the physical processes by which water escapes into space. Toward this goal, the absolute calibration of the instrument is critical for determining the D and H densities, the D/H ratio, and the escape flux of water. The instrument made observations of interplanetary hydrogen (IPH) along multiple look directions and conducted several postlaunch calibration campaigns during cruise as well as during orbit around Mars. The calibration efforts monitored instrument degradation and produced a consistent calibration factor at the hydrogen Lyman α wavelength (121.567 nm). The instrument was calibrated with the diffuse emission of interplanetary hydrogen (IPH) as a standard candle using measurements and model results from the Solar Wind Anisotropies (SWAN) instrument. Validation of the calibrated instrument was made by (1) comparisons to simultaneous observations of the IPH made with the lower resolution FUV mode of the IUVS instrument that were independently calibrated by using standard stars and by (2) comparisons to same‐day observations of Mars at hydrogen Lyman α made with the Hubble Space Telescope that were calculated with a radiative transfer model. Adopted FUV mode values and Hubble Space Telescope‐based model results agreed with the echelle SWAN calibrated values to within 6% and 4%, respectively. The calibrated IUVS instrument can be used to interpret emissions of atmospheric species at Mars for insights into water evolution at the planet, as well as observed IPH measurements made during cruise for further insights into dynamics of the inner heliosphere.

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In this paper, we perform numerical modeling of the interstellar hydrogen fluxes measured by IBEX-Lo during orbit 23 (spring 2009) using a state-of-the-art kinetic model of the interstellar neutral hydrogen distribution in the heliosphere.This model takes into account the temporal and heliolatitudinal variations of the solar parameters as well as non-Maxwellian kinetic properties of the hydrogen distribution due to charge exchange in the heliospheric interface.We found that there is a qualitative difference between the IBEX-Lo data and the modeling results obtained with the three-dimensional, time-dependent model. Namely, the model predicts a larger count rate in energy bin 2 (20-41 eV) than in energy bin 1 (11-21 eV), while the data shows the opposite case.We perform study of the model parameter effects on the IBEX-Lo fluxes and the ratio of fluxes in two energy channels. We shown that the most important parameter, which has a major influence on the ratio of the fluxes in the two energy bins, is the solar radiation pressure. The parameter fitting procedure shows that the best agreement between the model result and the data occurs in the case when the ratio of the solar radiation pressure to the solar gravitation, µ 0 , is 1.26 +0.06 −0.076 , and the total ionization rate of hydrogen at 1 AU is β E,0 = 3.7 +0.39 −0.35 × 10 −7 s −1 . We have found that the value of µ 0 is much larger than µ 0 = 0.89, which is the value derived from the integrated solar Lyman-alpha flux data for the period of time studied. We discuss possible reasons for the differences.

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[1] Recently Sokół et al. (2012) have presented a reconstruction of heliolatitudinal and time variations of the solar wind speed and density. Method of the reconstruction was based on the following: (i) measurements of the interplanetary scintillations, (ii) OMNI-2 solar wind data in the ecliptic plane, and (iii) Ulysses solar wind data out of the ecliptic plane. In this paper we use hydrogen charge exchange rates derived from their results as input parameters to calculate the interstellar hydrogen distribution in the heliosphere in the frame of our 3-D time-dependent kinetic model. The hydrogen distribution is then used to calculate the backscattered solar Lyman-alpha intensity maps. The theoretical Lyman-alpha maps are compared with the SOHO/SWAN measurements during maximum and minimum of the solar cycle activity. We found that in the solar minimum there is a quite good agreement between the model results and the SWAN data, but in the solar maximum sky maps of the Lyman-alpha, intensities are qualitatively different for the model results and observations. Physical reasons of the differences are discussed.