Interstellar neutral helium in the heliosphere from IBEX observations. IV. Flow vector, Mach number, and abundance of the Warm Breeze

Abstract

With the velocity vector and temperature of the pristine interstellar neutral (ISN) He recently obtained with high precision from a coordinated analysis summarized by McComas et al.2015b, we analyzed the IBEX observations of neutral He left out from this analysis. These observations were collected during the ISN observation seasons 2010---2014 and cover the region in the Earth's orbit where the Warm Breeze persists. We used the same simulation model and a very similar parameter fitting method to that used for the analysis of ISN He. We approximated the parent population of the Warm Breeze in front of the heliosphere with a homogeneous Maxwell-Boltzmann distribution function and found a temperature of $\sim 9500$ K, an inflow speed of 11.3 km s${}^{-1}$, and an inflow longitude and latitude in the J2000 ecliptic coordinates $251.6^{\circ }$, $12.0^{\circ }$. The abundance of the Warm Breeze relative to the interstellar neutral He is 5.7\% and the Mach number is 1.97. The newly found inflow direction of the Warm Breeze, the inflow directions of ISN H and ISN He, and the direction to the center of IBEX Ribbon are almost perfectly co-planar, and this plane coincides within relatively narrow statistical uncertainties with the plane fitted only to the inflow directions of ISN He, ISN H, and the Warm Breeze. This co-planarity lends support to the hypothesis that the Warm Breeze is the secondary population of ISN He and that the center of the Ribbon coincides with the direction of the local interstellar magnetic field. The common plane for the direction of inflow of ISN gas, ISN H, the Warm Breeze, and the local interstellar magnetic field %includes the Sun and is given by the normal direction: ecliptic longitude $349.7^{\circ }\pm 0.6^{\circ }$ and latitude $35.7^{\circ }\pm 0.6^{\circ }$ in the J2000 coordinates, with the correlation coefficient of 0.85.

Accepted for publication in Astrophysical Journal Supplement Series

References in corpus (15)

• Three-dimensional kinetic-MHD model of the global heliosphere with the heliopause-surface fitting
• 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
• Probing Heliospheric Asymmetries with an MHD-kinetic Model
• Warm Breeze from the starboard bow: a new population of neutral helium in the heliosphere
• Revisiting Ulysses Observations of Interstellar Helium
• Solar parameters for modeling interplanetary background
• Local Interstellar Neutral Hydrogen sampled in-situ by IBEX
• The Chemical Composition and Gas-to-Dust Mass Ratio of Nearby Interstellar Matter
• Neutral interstellar He parameters in front of the heliosphere 1994--2007
• Charting the Interstellar Magnetic Field causing the Interstellar Boundary Explorer (IBEX) Ribbon of Energetic Neutral Atoms
• Interstellar neutral helium in the heliosphere from IBEX observations. II. The Warsaw Test Particle Model (WTPM)
• Interstellar Neutral Helium in the Heliosphere from IBEX Observations. I. Uncertainties and Backgrounds in the Data and Parameter Determination Method
• Interstellar hydrogen fluxes measured by IBEX-Lo in 2009: numerical modeling and comparison with the data
• The Interstellar Neutral He haze in the heliosphere: what can we learn?
• Assessment of detectability of neutral interstellar deuterium by IBEX observations

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