INTERSTELLAR NEUTRAL HELIUM IN THE HELIOSPHERE FROM
                    <i>IBEX</i>
                    OBSERVATIONS. II. THE WARSAW TEST PARTICLE MODEL (WTPM)

Sokół, J. M.; Kubiak, M. A.; Bzowski, M.; Swaczyna, P.

doi:10.1088/0067-0049/220/2/27

Cited by 59 publications

(65 citation statements)

References 47 publications

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“…This probability assumes that the ionization rate is constant at a given location and falls off with the inverse square of the heliocentric radius, which is appropriate for photoionization and charge-exchange losses on average. Sokół et al (2015b) describe many details that are similar to our model's implementation, including the formulation of Kepler hyperbolic trajectories and the challenges that this type of modeling must address.…”

Section: Integrated Instrument Response Model Using Analytic Trajectomentioning

confidence: 99%

“…These details are important because the model is not restricted in spin-axis to orientations within the ecliptic or to exact Sun-pointing, and the frame of reference is precisely that of the sensor. (See Sokół et al 2015b for the effect of pointing variation on the observed He rate distributions as a function of the spin-phase and observer longitude.) We have performed numerous validation exercises, several of which we detail here.…”

Section: Observational Analysismentioning

confidence: 99%

“…The formulae for these transformations can be found in Lee et al (2012) and Sokół et al (2015b). The distribution function at the spacecraft is equated with the distribution function outside the heliosphere multiplied by the survival probability.…”

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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: Integrated Instrument Response Model Using Analytic Trajectomentioning

confidence: 99%

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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“…Kubiak et al (2016) analyzed the IBEX-Lo observations with E-step 2 during the early ISN observation seasons 2010-2014 (from mid-November to mid-January of each of those years) and unlike us, assumed that the entire observed signal is due to helium atoms. Using the Warsaw Test Particle model (Sokół et al 2015), they simulated a superposition of neutral He fluxes at Earthʼs orbit originating from two Maxwell-Boltzmann populations of He atoms in the outer heliosheath. They derived the flow parameters of the Warm Breeze through the parameter-fitting method by Swaczyna et al (2015).…”

Section: 7 Ismmentioning

confidence: 99%

Ibex Observations of Secondary Interstellar Helium and Oxygen Distributions

Park

Kucharek

Möbius

et al. 2016

ApJ

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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.

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“…Beyond this distance, the parameters of these two populations were assumed invariable with time and homogeneous in space. With this, Kubiak et al (2016) fitted the inflow direction and speed, temperature, and density of the Warm Breeze using the nWTPM simulation model (Sokół et al 2015) and data analysis method from Swaczyna et al (2015).…”

Section: Introductionmentioning

confidence: 99%

Distribution Function of Neutral Helium outside and inside the Heliopause

Kubiak

Bzowski

Sokół

2019

ApJ

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Interaction of the solar wind with interstellar matter involves, among other, charge exchange between interstellar neutral atoms and plasma, which results in the creation of secondary population of interstellar neutral (ISN) atoms. The secondary population of interstellar He was detected by Interstellar Boundary Explorer (IBEX), but interpretation of these measurements was mostly based on an approximation that the primary interstellar neutral population and the secondary population were non-interacting homogeneous Maxwell-Boltzmann functions in the outer heliosheath. We simulate the distribution function in the outer heliosheath and inside the heliopause using method of characteristics with statistical weights obtained from solutions of the production and loss equations for the secondary atoms due to charge-exchange collisions in the outer heliosheath. We show that the two-Maxwellian approximation for the distribution function of neutral He is not a good approximation within the outer heliosheath but a reasonable one inside the termination shock. This is due to a strong selection effect: the He atoms able to penetrate inside the termination shock are a small, peculiar subset of the entire secondary He population. Nevertheless, the two-Maxwellian approximation reproduces the density distribution of ISN He inside the termination shock well and enables a realistic reproduction of the orientation of the plane defined by the Sun's velocity vector through the local interstellar matter and the vector of unperturbed interstellar magnetic field.

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INTERSTELLAR NEUTRAL HELIUM IN THE HELIOSPHERE FROM IBEX OBSERVATIONS. II. THE WARSAW TEST PARTICLE MODEL (WTPM)

Cited by 59 publications

References 47 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

Ibex Observations of Secondary Interstellar Helium and Oxygen Distributions

Distribution Function of Neutral Helium outside and inside the Heliopause

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