FIRST SKY MAP OF THE INNER HELIOSHEATH TEMPERATURE USING<i>IBEX</i>SPECTRA

Livadiotis, G.; McComas, D. J.; Dayeh, M. A.; Funsten, H. O.; Schwadron, N. A.

doi:10.1088/0004-637x/734/1/1

Cited by 106 publications

(95 citation statements)

References 41 publications

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“…However, the energy overlap of these populations is sufficient to produce an apparent continuous ENA spectrum described by a single power law. Livadiotis et al (2011) used the fact that the spectrum from ∼0.7 to 6 keV can be characterized by a kappa distribution to derive temperatures and densities for the parent ion distribution in the inner heliosheath. The temperatures were quite low (2.2 × 10 5 K in the V1 direction in the sky), indicating that the kappa distribution is effectively extended to energies well below 0.7 keV.…”

Section: Ena Fluxes At 100 Au and Implications For Inner Heliosheath mentioning

confidence: 99%

“…Although the plasma in the inner heliosheath is slowed and heated across the termination shock, on average, it is still moving away from the Sun with average radial bulk velocity of ∼100 km s −1 (Richardson & Wang 2011). Accounting for the reported ENA fluxes below 0.5 keV requires high ion densities in the heliosheath (∼0.1 cm −3 ) and significant slowing and diversion of the bulk ion flow (Livadiotis et al 2011(Livadiotis et al , 2013, high plasma turbulence in the heliosheath (Gloeckler & Fisk 2010), another source of low energy neutrals from outside the heliosheath (Desai et al 2014;Heerikhuisen, et al 2013), some combination of these possibilities, or another yet unspecified source.…”

Section: Introductionmentioning

confidence: 99%

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Low Energy Neutral Atoms From the Heliosheath

Fuselier

Allegrini

Bzowski

et al. 2014

ApJ

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In the heliosheath beyond the termination shock, low energy (<0.5 keV) neutral atoms are created by charge exchange with interstellar neutrals. Detecting these neutrals from Earth's orbit is difficult because their flux is reduced substantially by ionization losses as they propagate from about 100 to 1 AU and because there are a variety of other signals and backgrounds that compete with this weak signal. Observations from IBEX-Lo and -Hi from two opposing vantage points in Earth's orbit established a lower energy limit of about 0.1 keV on measurements of energetic neutral atoms (ENAs) from the heliosphere and the form of the energy spectrum from about 0.1 to 6 keV in two directions in the sky. Below 0.1 keV, the detailed ENA spectrum is not known, and IBEX provides only upper limits on the fluxes. However, using some assumptions and taking constraints on the spectrum into account, we find indications that the spectrum turns over at an energy between 0.1 and 0.2 keV.

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Section: Ena Fluxes At 100 Au and Implications For Inner Heliosheath mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Low Energy Neutral Atoms From the Heliosheath

Fuselier

Allegrini

Bzowski

et al. 2014

ApJ

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“…A well-defined temperature must be uniquely defined, and the fact of the equivalence of the two definition leads to a meaningful temperature for systems out of thermal equilibrium that are described by kappa distributions. (For more details on this topic, see Livadiotis and McComas 2009, 2010a, 2011b, 2012, 2013b; see also Livadiotis 2009;Livadiotis et al 2011Livadiotis et al , 2013 4.7. Isotropic Debye shielding In all the above, we have assumed that the Debye length is isotropic, namely, it is the same for any direction Ω ≡ (ϑ, ϕ).…”

Section: No Correlations Between Ions and Electronsmentioning

confidence: 99%

“…Christon 1987;Collier and Hamilton 1995;Grabbe 2000;Mauk et al 2004;Schippers et al 2008;Dialynas et al 2009;Ogasawara et al 2013), outer heliosphere and inner heliosheath (e.g. Decker and Krimigis 2003;Decker et al 2005;Heerikhuisen et al 2008;Zank et al 2010;Livadiotis et al 2011Livadiotis et al , 2013, and other general plasma analyses (e.g. Milovanov …”

Section: Introductionmentioning

confidence: 99%

Electrostatic shielding in plasmas and the physical meaning of the Debye length

Livadiotis

McComas

2014

J. Plasma Phys.

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This paper examines the electrostatic shielding in plasmas, and resolves inconsistencies about what the Debye length really is. Two different interpretations of the Debye length are currently used: (1) The potential energy approximately equals the thermal energy, and (2) the ratio of the shielded to the unshielded potential drops to 1/e. We examine these two interpretations of the Debye length for equilibrium plasmas described by the Boltzmann distribution, and non-equilibrium plasmas (e.g. space plasmas) described by kappa distributions. We study three dimensionalities of the electrostatic potential: 1-D potential of linear symmetry for planar charge density, 2-D potential of cylindrical symmetry for linear charge density, and 3-D potential of spherical symmetry for a point charge. We resolve critical inconsistencies of the two interpretations, including: independence of the Debye length on the dimensionality; requirement for small charge perturbations that is equivalent to weakly coupled plasmas; correlations between ions and electrons; existence of temperature for nonequilibrium plasmas; and isotropic Debye shielding. We introduce a third Debye length interpretation that naturally emerges from the second statistical moment of the particle position distribution; this is analogous to the kinetic definition of temperature, which is the second statistical moment of the velocity distribution. Finally, we compare the three interpretations, identifying what information is required for theoretical/experimental plasma-physics research: Interpretation 1 applies only to kappa distributions; Interpretation 2 is not restricted to any specific form of the ion/electron distributions, but these forms have to be known; Interpretation 3 needs only the second statistical moment of the positional distribution.

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“…thermal solar wind, pick-up ions) of the plasma flow in this region (see e.g. Zank et al 2010;Livadiotis et al 2011;Siewert et al 2013). In contrast to this, identifying a possible modulation of more distant sources beyond the heliopause is less trivial because of the specific configurations and assumptions used by models devoted to these sources (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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FIRST SKY MAP OF THE INNER HELIOSHEATH TEMPERATURE USINGIBEXSPECTRA

Cited by 106 publications

References 41 publications

Low Energy Neutral Atoms From the Heliosheath

Low Energy Neutral Atoms From the Heliosheath

Electrostatic shielding in plasmas and the physical meaning of the Debye length

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

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