Ibex Observations of Secondary Interstellar Helium and Oxygen Distributions

Abstract

In this study, we investigate the directional distributions of the secondary interstellar neutral (ISN) He and O populations at Earthʼs orbit. The secondary populations are created by charge exchange between ISN atoms and interstellar ions in the outer heliosheath. Using the IBEX-Lo He and O observations during the winter-spring seasons (early December to early June) in 2009-2011, we produced all-sky maps for He and O atoms with sputtering corrections. These sky maps include the directional distributions of the primary ISN gas and secondary populations. Our investigations reveal that the secondary He and O populations are observed in the ecliptic longitude range 160°-210°. The peak longitudes of the secondary He and O appear to be 14°-34°and 38°-43°a way from the peak longitude of the primary interstellar gas flow, respectively. These results indicate that the secondary populations have lower bulk speeds relative to the Sun and their flow directions deviate from the primary gas flow. These results may indicate that one side of the outer heliosheath is thicker than the other side relative to the flow direction of the primary interstellar gas flow.

Science Opportunities from Observations of the Interstellar Neutral Gas with Adjustable Boresight Direction

“…In the case of Ne and O we consider only one: the primary, population. The secondary population of ISN O has been detected based on IBEX -Lo measurements by Park et al (2016); Baliukin et al (2017); Park et al (2019). However, the abundance ratios of secondary to primary O obtained from data analysis and modeling differ significantly.…”

“…The secondary populations are products of charge exchange between the ISN atoms and ions in OHS(Baranov & Malama 1993). The secondary populations of H(Lallement et al 2005), HeKubiak et al 2014), and O(Park et al 2016) have been discovered in the heliosphere. Thus far, the secondary populations could only be analyzed based on the IBEX -Lo(Kubiak et al 2016;Bzowski et al 2017;Baliukin et al 2017;Kubiak et al 2019;Park et al 2019) and Ulysses(Wood et al 2017) measurements.…”

Turbulence in the Local Interstellar Medium and the IBEX Ribbon

“…The Interstellar Boundary Explorer (IBEX; McComas et al 2009a) is an Earth-orbiting spacecraft with two single-pixel cameras (Funsten et al 2009;Fuselier et al 2009) that detect interstellar neutral atoms flowing into the heliosphere from the VLISM (e.g., Bzowski et al 2017;Kubiak et al 2016;McComas et al 2015;Möbius et al 2009;Park et al 2016;Schwadron et al 2016) and ENAs produced by charge-exchange in the outer heliosphere (e.g., McComas et al 2009bMcComas et al , 2017McComas et al , 2018bDesai et al 2019;Schwadron et al 2018). Full-sky observations of neutral atoms provide a means to deduce the thermodynamic and structural properties of the outer heliosphere and its interaction with the VLISM (e.g., Bzowski et al 2017;Zirnstein et al 2017).…”

An Empirical Model of Energetic Neutral Atom Imaging of the Heliosphere and Its Implications for Future Heliospheric Missions at Great Heliocentric Distances

“…This allows us to make some predictions for an ENA instrument onboard a spacecraft at heliocentric distances beyond Mars orbit. Interstellar neutral (ISN) He, H, and other ISN species flowing into the heliosphere (Müller & Zank 2004;Witte 2004;Möbius et al 2012;Rodríguez et al 2012;Saul et al 2012;Kubiak et al 2014;McComas et al 2015;Park et al 2016;Galli et al 2019) could also be measured with ENA cameras such as IBEX-Lo (Fuselier et al 2009) or with a mass spectrometer (Barabash et al 2019). However, we have to relegate questions about ISN observation strategies to a future publication because our heliosphere model currently does not include ISN trajectories.…”