Comparison of Interstellar Boundary Explorer Observations with 3D Global Heliospheric Models

Schwadron, N. A.; Bzowski, M.; Crew, G. B.; Gruntman, M.; Fahr, H. J.; Fichtner, H.; Frisch, P. C.; Funsten, H. O.; Fuselier, S. A.; Heerikhuisen, J.; Izmodenov, Vladislav; Kucharek, H.; Lee, M.; Livadiotis, G.; McComas, D. J.; Möbius, E.; Moore, T.E.; Mukherjee, J.; Pogorelov, N. V.; Prested, C.; Reisenfeld, D. B.; Roelof, E. C.; Zank, G. P.

doi:10.1126/science.1180986

Cited by 229 publications

(261 citation statements)

References 18 publications

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“…Detecting energetic neutral atoms (ENAs) generated in the outer heliosphere provides a new window into the otherwise inaccessible plasma physics at the borders of the solar system. Since the first release of the IBEX data (McComas et al 2009a;Schwadron et al 2009;Funsten et al 2009;Fuselier et al 2009), it became obvious that essentially all existing models of the heliospheric interface disagreed with the new observational data. Many new models, ideas and concepts related to the outer heliosphere have been put forward since (see e.g.…”

Section: Introductionmentioning

confidence: 99%

Transit-time aspects of ENA production models for the inner heliosheath

Siewert

Fahr

McComas

2014

A&A

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It is still a major challenge to understand the data of energetic neutral atoms (ENAs) that arrive from the outer heliosphere. These data are provided by the IBEX mission. With the most recent data covering three years of dynamical evolution, it is now possible to study temporal correlations with the solar cycle. We present in this paper for the first time an extended study dedicated to the transit-time delay between the plasma that is ejected from the Sun towards the outer heliosphere and the ENA fluxes that reach the detector after the solar wind protons undergo charge exchange processes in their distant production regions in the inner heliosheath. We derive transit-time delays caused by both general and non-trivial model-dependent contributions for arbitrary points in the inner heliosheath. In addition, we also calculate the average transit-time delay along the line-of-sight in selected directions, allowing to estimate how strongly an extended emission region can reduce the resolution that is possible with transit-time studies. We are able to demonstrate that ENAs generated beyond a certain characteristic streamline distance are mostly removed by charge exchange, and thus do not contribute significantly to the keV-ENA fluxes observed by IBEX. For this reason, transit-time delays do provide a viable tool for studying the impact of the solar cycle on ENA fluxes.

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Section: Introductionmentioning

confidence: 99%

Transit-time aspects of ENA production models for the inner heliosheath

Siewert

Fahr

McComas

2014

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“…The first global IBEX observations (McComas et al 2009b;Fuselier et al 2009;Funsten et al 2009a;Schwadron et al 2009) revealed a narrow Ribbon of ENA emission, 2-3 times brighter than the global distribution of ENAs. This Ribbon is only ∼20 • in width, but extends over the sky (being brighter along a ∼300 • arc across the sky).…”

Section: Introductionmentioning

confidence: 99%

“…This Ribbon is only ∼20 • in width, but extends over the sky (being brighter along a ∼300 • arc across the sky). Several ideas regarding its possible sources were discussed by McComas et al (2009b), with additional analysis for some of these performed by Schwadron et al (2009), Funsten et al (2009a), and McComas et al (2010. The time variation and large-scale stability of the outer heliosphere was examined by McComas et al (2010) who compared the second to the first sets of sky maps (after inclusion of Compton-Getting corrections for the spacecraft motion).…”

Section: Introductionmentioning

confidence: 99%

FIRST SKY MAP OF THE INNER HELIOSHEATH TEMPERATURE USINGIBEXSPECTRA

Livadiotis

McComas

Dayeh

et al. 2011

ApJ

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106

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Analysis of the IBEX-Hi Energetic Neutral Atom spectra reveals, for the first time, the sky map of the source ion temperatures. The solar wind exists in non-equilibrium stationary states and can be described by kappa distributions. The high-energy asymptotic behavior of kappa distributions leads to a power law of the flux versus energy spectrum, while its specific formulation derives the temperature and kappa index that govern these distributions. We find that the observed temperature in most directions is about a million degrees, in agreement with most heliospheric models for the inner heliosheath. Thus, the termination shock is stronger in most places than revealed by the Voyagers' observations at their two unique crossing points. The global sky maps indicate low-temperature regions in various directions, including toward Voyager 2 where the temperature is an order of magnitude lower, consistent with in situ Voyager observations. Interestingly, the vast majority of measured kappa indices are between ∼1.5 and ∼2.5, consistent with the far-equilibrium "cavity" of minimum entropy discovered by Livadiotis & McComas. The sky maps suggest that the Ribbon is a string of localized regions, while its thermodynamical behavior differentiates it from the global distributed flux. A simple model is developed to derive the density, heliosheath thickness, and thermal pressure. We find that the Ribbon thermal pressure is ∼3.5 pDyn cm −2 , roughly equal to the mechanical pressure exerted by the Local Interstellar Medium.

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“…Although we concentrate on particles in the HSTOF energy range, we extend our calculations also to lower energies to compare to the IBEX Schwadron et al 2009Schwadron et al , 2011 and INCA (Krimigis et al 2009(Krimigis et al , 2010(Krimigis et al , 2011 ENA data. We comment briefly on the relation between the lowenergy data and the observations by HSTOF.…”

Section: Introductionmentioning

confidence: 99%

HSTOF ENA observations and energetic ion distributions in the heliosheath

Czechowski

Hilchenbach

Hsieh

2012

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Context. Launched in 1996, HSTOF on board SOHO was the first instrument to detect the energetic neutral atoms (ENA) from the heliosheath. After mid 2003, the field of view of HSTOF was restricted to the flank sectors of the heliosheath, in which region the energetic ion distributions are still unknown. Interpretation of these data requires understanding of the energetic ion transport in the inner heliosheath. Aims. We update the HSTOF ENA hydrogen and helium spectra by adding the results from the recent (2006−2010) measurements. We calculate the energetic ion distributions in a numerical model of the heliosheath and use them as a basis for interpreting the HSTOF ENA observations, in particular those of the flank sectors. Methods. The hydrogen and helium ENA spectra were derived from the HSTOF observations of two 90 • -wide ecliptic longitude sectors around the crosswind directions. The energetic ion distributions in the heliosheath were calculated in a simple model of the heliosphere, assuming that the main acceleration occurs at the termination shock. The effects of different processes (charge-exchange loss, adiabatic acceleration, parallel diffusion and escape across the boundary) were determined with different assumptions about the boundary conditions and the transport parameters. The resulting ion distributions were used to calculate the ENA fluxes, which can be compared with the observations by HSTOF and other instruments. Results. The energetic ion density in the flank sectors of the heliosphere is lower than in the forward (upwind) sector. As a result, the contribution of the flanks of the heliosheath to the production of ENA is not directly proportional to the thickness of the heliosheath, but instead is comparable to the contribution of the forward sector, which agrees with the HSTOF data. The HSTOF ENA flux intensity is nevertheless significantly lower than the model calculations. Near the heliopause there appears a region of low energetic ion density caused by the charge-exchange and the escape losses.

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Comparison of Interstellar Boundary Explorer Observations with 3D Global Heliospheric Models

Cited by 229 publications

References 18 publications

Transit-time aspects of ENA production models for the inner heliosheath

Transit-time aspects of ENA production models for the inner heliosheath

FIRST SKY MAP OF THE INNER HELIOSHEATH TEMPERATURE USINGIBEXSPECTRA

HSTOF ENA observations and energetic ion distributions in the heliosheath

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