Correcting the record on the analysis of IBEX and STEREO data regarding variations in the neutral interstellar wind

Abstract

The journey of the Sun through space carries the solar system through a dynamic interstellar environment that is presently characterized by Mach 1 motion between the heliosphere and the surrounding interstellar medium (ISM). The interaction between the heliosphere and ISM is an evolving process due to the variable solar wind and to interstellar turbulence. Frisch et al. presented a meta-analysis of the historical data on the interstellar wind flowing through the heliosphere and concluded that temporal changes in the ecliptic longitude of the wind were statistically indicated by the data available in the refereed literature at the time of that writing. Lallement and Bertaux disagree with this result, and suggested, for instance, that a key instrumental response function of IBEX-Lo was incorrect and that the STEREO pickup ion data are unsuitable for diagnosing the flow of interstellar neutrals through the heliosphere. Here we show that temporal variations in the interstellar wind through the heliosphere are consistent with our knowledge of local ISM. The statistical analysis of the historical helium wind data is revisited, and a recent correction of a typographical error in the literature is incorporated into the new fits. With this correction, and including no newer IBEX results, these combined data still indicate that a change in the longitude of the interstellar neutral wind over the past forty years is statistically likely, but that a constant flow longitude is now also statistically possible. It is shown that the IBEX instrumental response function is known, and that the STEREO pickup ion data have been correctly utilized in this analysis.

arXiv commentAstrophysical Journal, in press

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Cited by in corpus (9)

• Interstellar neutral helium in the heliosphere from IBEX observations. III. Mach number of the flow, velocity vector, and temperature from the first six years of measurements
• Charting the Interstellar Magnetic Field causing the Interstellar Boundary Explorer (IBEX) Ribbon of Energetic Neutral Atoms
• The interface between the outer heliosphere and the inner lism: Morphology of the local interstellar cloud, its hydrogen hole, stromgren shells, and ${}^{60}$Fe accretion
• Interstellar Neutral Helium in the Heliosphere from IBEX Observations. I. Uncertainties and Backgrounds in the Data and Parameter Determination Method
• Very Local Interstellar Medium Revealed by Complete Solar Cycle of Interstellar Neutral Helium Observations with IBEX
• Draping of the Interstellar Magnetic Field over the Heliopause - A Passive Field Model
• Solar cycle variation of interstellar neutral He, Ne, O density and pick-up ions along the Earth's orbit
• Interstellar Conditions Deduced from Interstellar Neutral Helium Observed by IBEX and Global Heliosphere Modeling
• Science Opportunities from Observations of the Interstellar Neutral Gas with Adjustable Boresight Direction