INTERSTELLAR NEUTRAL HELIUM IN THE HELIOSPHERE FROM
                    <i>IBEX</i>
                    OBSERVATIONS. III. MACH NUMBER OF THE FLOW, VELOCITY VECTOR, AND TEMPERATURE FROM THE FIRST SIX YEARS OF MEASUREMENTS

Bzowski, M.; Swaczyna, P.; Kubiak, M. A.; Sokół, J. M.; Fuselier, S. A.; Galli, André; Heirtzler, D.; Kucharek, H.; Leonard, T.; McComas, D. J.; Möbius, E.; Schwadron, N. A.; Würz, Peter

doi:10.1088/0067-0049/220/2/28

Cited by 108 publications

(107 citation statements)

References 54 publications

(193 reference statements)

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“…This reinforces the hypothesis that the Warm Breeze may strongly influence data in 2014 when spin-axis tilts are well below the ecliptic. The data in 2014 remains under active investigation and is studied by Bzowski et al (2015), but is not included in this 2 c minimization.…”

Section: Observational Analysismentioning

confidence: 99%

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DETERMINATION OF INTERSTELLAR He PARAMETERS USING FIVE YEARS OF DATA FROM THE IBEX : BEYOND CLOSED FORM APPROXIMATIONS

Schwadron

Möbius

Leonard

et al. 2015

ApJS

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Interstellar He represents a key sample of interstellar matter that, due to its high first ionization potential, survives the journey from beyond our solar system's heliospheric boundaries to Earth. Ongoing analysis of interstellar neutral (ISN) He atoms by the Interstellar Boundary Explorer (IBEX) has resulted in a growing sophistication in our understanding of the local interstellar flow. A key feature of the IBEX observations near perihelion of the ISN trajectories is a narrow "tube" of approximately degenerate interstellar parameters. These degenerate solutions provide a tightly coupled relationship between the interstellar flow longitude and latitude, speed, and temperature. However, the IBEX analysis resulting in a specific solution for the inflow longitude, inflow speed, temperature, and inflow latitude was accompanied by a sizeable uncertainty along the parameter tube. Here, we use the three-step method to find the interstellar parameters: (1) the ISN He peak rate in ecliptic longitude uniquely determines a relation (as part of the tube in parameter space) between the longitude ISN l ¥ and the speed V ISN¥ of the He ISN flow at infinity; (2) the ISN He peak latitude (on the great circle swept out in each spin) is compared to simulations to derive unique values for ISN l ¥ and V ISN¥ along the parameter tube; and (3) the angular width of the He flow distributions as a function of latitude is used to derive the interstellar He temperature. For simulated peak latitudes, we use a relatively new analytical tool that traces He atoms from beyond the termination shock into the position of IBEX and incorporates the detailed response function of IBEX-Lo. By varying the interstellar parameters along the IBEX parameter tube, we find the specific parameters that minimize the chi-square difference between observations and simulations. The new computational tool for simulating neutral atoms through the integrated IBEX-Lo response function makes no assumptions or expansions with respect to the spin-axis pointing or frame of reference. Thus, we are able to move beyond closed-form approximations and utilize observations of interstellar He during the complete five year period from 2009 to 2013 when the primary component of interstellar He is most prominent. Chi-square minimization of simulations compared to observations results in a He ISN flow longitude of 75 6 ± 1 4, latitude of −5 12 ± 0 27, speed of 25.4 ± 1.1 km s −1 , and temperature of 8000 ± 1300 K, where the uncertainties are related and apply along the IBEX parameter tube. This paper also provides documentation for a new release of ISN data and associated model runs.

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Section: Observational Analysismentioning

confidence: 99%

“…Additional IBEX data products and results spanning the coordinated set of papers in the Special Issue on ISNs are included in the release, as also documented by Swaczyna et al (2015) and Bzowski et al (2015).…”

Section: Data Releasementioning

confidence: 99%

DETERMINATION OF INTERSTELLAR He PARAMETERS USING FIVE YEARS OF DATA FROM THE IBEX : BEYOND CLOSED FORM APPROXIMATIONS

Schwadron

Möbius

Leonard

et al. 2015

ApJS

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“…Ulysses and IBEX (Witte 2004;Bzowski et al 2015;McComas et al 2015). It was shown that the pristine LISM flow is supersonic and one would expect a bow shock to be formed in front of the HP.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional Features of the Outer Heliosphere Due to Coupling between the Interstellar and Heliospheric Magnetic Field. V. The Bow Wave, Heliospheric Boundary Layer, Instabilities, and Magnetic Reconnection

Pogorelov

Heerikhuisen

Roytershteyn

et al. 2017

ApJ

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The heliosphere is formed due to interaction between the solar wind (SW) and local interstellar medium (LISM). The shape and position of the heliospheric boundary, the heliopause, in space depend on the parameters of interacting plasma flows. The interplay between the asymmetrizing effect of the interstellar magnetic field and charge exchange between ions and neutral atoms plays an important role in the SW-LISM interaction. By performing three-dimensional, MHD plasma / kinetic neutral atom simulations, we determine the width of the outer heliosheath -the LISM plasma region affected by the presence of the heliosphere -and analyze quantitatively the distributions in front of the heliopause.It is shown that charge exchange modifies the LISM plasma to such extent that the contribution of a shock transition to the total variation of plasma parameters becomes small even if the LISM velocity exceeds the fast magnetosonic speed in the unperturbed medium. By performing adaptive mesh refinement simulations, we show that a distinct boundary layer of decreased plasma density and enhanced magnetic field should be observed on the interstellar side of the heliopause. We show that this behavior is in agreement with the plasma oscillations of increasing frequency observed by the plasma wave instrument onboard Voyager 1. We also demonstrate that Voyager observations in the inner heliosheath between the heliospheric termination shock and the heliopause are consistent with dissipation of the heliospheric magnetic field. The choice of LISM parameters in this analysis is based on the simulations that fit observations of energetic neutral atoms performed by IBEX.

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“…One can similarly partition the VLISM energy into various proton populations . The VLISM plasma consists mostly of protons, initially ∼7500 K in the pristine LISM Schwadron et al 2015;Bzowski et al 2015), that are partially heated by charge exchange near the H wall and by crossing a bow wave Zank et al 2013). However, the increase in thermal energy of the VLISM plasma near the HP is also due to energetic PUIs, which are created from charge exchange between LISM protons and ENAs from the IHS .…”

Section: Selected Observationsmentioning

confidence: 99%

“…It was noted that energetic neutral H created via charge exchange in the IHS and fast solar wind could "splash" back into the interstellar medium where they would experience a secondary charge exchange. The secondary charge exchange of hot and/or fast neutral H with cold (∼7500 K-McComas et al (2012K-McComas et al ( , 2015; Schwadron et al (2015); Bzowski et al (2015) LISM protons leads to the creation of a hot or suprathermal PUI population locally in region 1. The heating of the LISM in the neighborhood of the Sun has been discussed in detail (Zank et al 2013), since this results in an increased sound speed with a concomitant weakening or even elimination of the bow shock (yielding instead a bow wave) .…”

Section: Introductionmentioning

confidence: 99%

Pickup ion-mediated plasma physics of the outer heliosphere and very local interstellar medium

Zank

2016

Geosci. Lett.

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Observations of plasma and turbulence in the outer heliosphere (the distant supersonic solar wind and the subsonic solar wind beyond the heliospheric termination shock) made by the Voyager Interstellar Mission and the energetic neutral atom observations made by the IBEX spacecraft have revealed that the underlying plasma in the outer heliosphere and very local interstellar medium (VLISM) comprises distinct thermal proton and electron and suprathermal pickup ion (PUI) populations. Estimates of the appropriate collisional frequencies show that the multi-component plasma is not collisionally equilibrated in either the outer heliosphere or VLISM. Furthermore, suprathermal PUIs in these regions form a thermodynamically dominant component. We review briefly a subset of the observations that led to the realization that the solar wind-VLISM interaction region is described by a non-equilibrated multi-component plasma and summarizes the derivation of suitable plasma models that describe a PUI-mediated plasma.

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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

Cited by 108 publications

References 54 publications

DETERMINATION OF INTERSTELLAR He PARAMETERS USING FIVE YEARS OF DATA FROM THE IBEX : BEYOND CLOSED FORM APPROXIMATIONS

DETERMINATION OF INTERSTELLAR He PARAMETERS USING FIVE YEARS OF DATA FROM THE IBEX : BEYOND CLOSED FORM APPROXIMATIONS

Three-dimensional Features of the Outer Heliosphere Due to Coupling between the Interstellar and Heliospheric Magnetic Field. V. The Bow Wave, Heliospheric Boundary Layer, Instabilities, and Magnetic Reconnection

Pickup ion-mediated plasma physics of the outer heliosphere and very local interstellar medium

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