Structures and Spectral Variations of the Outer Heliosphere in IBEX Energetic Neutral Atom Maps

Funsten, H. O.; Allegrini, F.; Crew, G. B.; Demajistre, R.; Frisch, P. C.; Fuselier, S. A.; Gruntman, M.; Janzen, P. H.; McComas, D. J.; Möbius, E.; Randol, B. M.; Reisenfeld, D. B.; Roelof, E. C.; Schwadron, N. A.

doi:10.1126/science.1180927

Cited by 199 publications

(222 citation statements)

References 17 publications

(21 reference statements)

Supporting

Mentioning

208

Contrasting

Order By: Relevance

“…For this reason in this paper, the statistical pressure is called thermal for any part of the spectrum, encompassing both the core and the tail. The thermal pressure in the region of the Ribbon was estimated by Funsten et al (2009a), using the ENA's flux emitted from these directions in space, and found to be comparable to the mechanical pressure exerted by the LISM as calculated by Schwadron et al (2009). Here we show that the thermal pressure is equal to the mechanical pressure, and this phenomenological equilibrium supports the stability of the Ribbon.…”

Section: Introductionsupporting

confidence: 76%

“…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%

See 2 more Smart Citations

FIRST SKY MAP OF THE INNER HELIOSHEATH TEMPERATURE USINGIBEXSPECTRA

Livadiotis

McComas

Dayeh

et al. 2011

ApJ

Self Cite

106

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionsupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

FIRST SKY MAP OF THE INNER HELIOSHEATH TEMPERATURE USINGIBEXSPECTRA

Livadiotis

McComas

Dayeh

et al. 2011

ApJ

Self Cite

106

View full text Add to dashboard Cite

show abstract

“…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

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…The IBEX payload consists of two single-pixel ENA cameras with large geometric factors, IBEX-Lo (Fuselier et al 2009a) and IBEX-Hi (Funsten et al 2009b), whose fields-of-view (FoV) point radially outward into two opposite directions and whose combined energy range is 10-6000 eV with an overlap between 300 and 2000 eV. A single combined electronics unit (CEU) controls these sensors, stores data, and is the payload interface to the spacecraft bus (McComas et al 2004(McComas et al , 2009a.…”

Section: Overview Of the Ibex Missionmentioning

confidence: 99%

Evidence of direct detection of interstellar deuterium in the local interstellar medium by IBEX

Moreno

Würz

Saul

et al. 2013

A&A

Self Cite

View full text Add to dashboard Cite

We report the first in situ measurements of neutral deuterium originating in the local interstellar medium (LISM) in Earth's orbit. These measurements were performed with the IBEX-Lo camera on NASA's interstellar boundary explorer (IBEX) satellite. All data from the spring observation periods of 2009 through 2011 have been analysed. In the three years of the IBEX mission time, the observation geometry and orbit allowed for a total observation time of 115.3 days for the LISM. However, the effects of the spinning spacecraft and the stepping through 8 energy channels mean that we are only observing the interstellar wind for a total time of 1.44 days, in which 2 counts for interstellar deuterium were collected. We report here a conservative number, because a possibility of systematic error or additional noise, though eliminated in our analysis to the best of our knowledge, only supports detection at a 1-sigma level. From these observations, we derive a ratio D/H = 5.8 ± 4.4 × 10 −4 at 1 AU. After modelling the transport and loss of D and H from the termination shock to Earth's orbit, we find that our result of D/H LISM = 1.6 ± 1.2 × 10 −5 agrees with D/H LIC = 1.6 ± 0.4 × 10 −5 for the local interstellar cloud. This weak interstellar signal is extracted from a strong terrestrial background signal consisting of sputter products from the sensor's conversion surface. As reference, we accurately measure the terrestrial D/H ratio in these sputtered products and then discriminate this terrestrial background source. Because of the diminishing D and H signal at Earth's orbit during the rising solar activity due to photoionisation losses and increased photon pressure, our result demonstrates that in situ measurements of interstellar deuterium in the inner heliosphere are only possible during solar minimum conditions.

show abstract

Structures and Spectral Variations of the Outer Heliosphere in IBEX Energetic Neutral Atom Maps

Cited by 199 publications

References 17 publications

FIRST SKY MAP OF THE INNER HELIOSHEATH TEMPERATURE USINGIBEXSPECTRA

FIRST SKY MAP OF THE INNER HELIOSHEATH TEMPERATURE USINGIBEXSPECTRA

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

Evidence of direct detection of interstellar deuterium in the local interstellar medium by IBEX

Contact Info

Product

Resources

About