Faltering Steps Into the Galaxy: The Boundary Regions of the Heliosphere

Zank, G. P.

doi:10.1146/annurev-astro-082214-122254

Cited by 132 publications

(101 citation statements)

References 212 publications

(332 reference statements)

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“…The study of the interaction between our Sun and the LISM led to a large literature, including, amongst other, numerical investigations of the bow shock formed by the solar wind (see, e.g. Pogorelov & Matsuda 1998;Baranov & Malama 1993;Zank 2015, and references therein). If obvious similitudes between the bow shock of the Sun and those of our massive stars indicate that the physical processes governing the formation of circumstellar nebulae around OB stars such as electronic thermal conduction or the influence of the background local magnetic field have to be included in the modelling of those structures (Zank et al 2009), nevertheless, the bow shock of the Sun is, partly due to the differences in terms of effective temperature and wind velocity, on a totally different scale.…”

Section: Comparison With the Bow Shock Around The Sunmentioning

confidence: 99%

Bow shock nebulae of hot massive stars in a magnetized medium

Meyer

Mignone

Kuiper

et al. 2016

Mon. Not. R. Astron. Soc.

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A significant fraction of OB-type, main-sequence massive stars are classified as runaway and move supersonically through the interstellar medium (ISM). Their strong stellar winds interact with their surroundings where the typical strength of the local ISM magnetic field is about 3.5-7 µG, which can result in the formation of bow shock nebulae. We investigate the effects of such magnetic fields, aligned with the motion of the flow, on the formation and emission properties of these circumstellar structures. Our axisymmetric, magneto-hydrodynamical simulations with optically-thin radiative cooling, heating and anisotropic thermal conduction show that the presence of the background ISM magnetic field affects the projected optical emission our bow shocks at Hα and [OIII] λ 5007 which become fainter by about 1-2 orders of magnitude, respectively. Radiative transfer calculations against dust opacity indicate that the magnetic field slightly diminishes their projected infrared emission and that our bow shocks emit brightly at 60 µm. This may explain why the bow shocks generated by ionizing runaway massive stars are often difficult to identify. Finally, we discuss our results in the context of the bow shock of ζ Ophiuchi and we support the interpretation of its imperfect morphology as an evidence of the presence of an ISM magnetic field not aligned with the motion of its driving star.

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Section: Comparison With the Bow Shock Around The Sunmentioning

confidence: 99%

Bow shock nebulae of hot massive stars in a magnetized medium

Meyer

Mignone

Kuiper

et al. 2016

Mon. Not. R. Astron. Soc.

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“…There is extensive theoretical literature which predicts that the pressure of pickup ions (primarily protons) is significantly greater than the magnetic pressure and the thermal pressure of the solar wind particles (Zank 2015). There is evidence that pickup ions make the dominant contribution to the pressure in the distant heliosphere ) and in the heliosheath (Richardson 2008;Richardson et al 2008;Krimigis et al 2010;Decker et al 2015).…”

Section: Structure and Formation Of The Interaction Regionmentioning

confidence: 99%

“…This MHD-Hall model includes pickup protons as well as protons, electrons, and neutral hydrogen. All of these components must be considered in the distant heliosphere and the heliosheath (Zank 2015). Avinash et al show that magnetic holes and humps can only exist if either the Mach number of the pickup protons 1 and greater than that of the solar wind ions (which is the case for the heliosheath), as shown by the observations of Richardson et al (2008) or the Mach number of the pickup ions is less than the Mach number of the solar wind ions which must be 1.…”

Section: Magnetic Humps and Magnetic Holesmentioning

confidence: 99%

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Heliosheath Magnetic Field and Plasma Observed by Voyager 2 During 2012 in the Rising Phase of Solar Cycle 24

Burlaga

Ness

Richardson

et al. 2016

ApJ

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We discuss magnetic field and plasma observations of the heliosheath made by Voyager 2 (V2) during 2012, when V2 was observing the effects of increasing solar activity following the solar minimum in 2009. The average magnetic field strength B was 0.14 nT and B reached 0.29 nT on day 249. V2 was in a unipolar region in which the magnetic polarity was directed away from the Sun along the Parker spiral 88% of the time, indicating that V2 was poleward of the heliospheric current sheet throughout most of 2012. The magnetic flux at V2 during 2012 was constant. A merged interaction region (MIR) was observed, and the flow speed increased as the MIR moved past V2. The MIR caused a decrease in the >70 MeV nuc −1 cosmic-ray intensity. The increments of B can be described by a q-Gaussian distribution with q=1.2±0.1 for daily averages and q=1.82±0.03 for hour averages. Eight isolated current sheets ("PBLs") and four closely spaced pairs of current sheets were observed. The average change of B across the current sheets was a factor of ≈2, and B increased or decreased with equal probability. Magnetic holes and magnetic humps were also observed. The characteristic size of the PBLs was ≈6 R L , where R L is the Larmor radius of protons, and the characteristic sizes of the magnetic holes and humps were ≈38 R L and ≈11 R L , respectively.

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“…Pluto's orbit lies in the outer heliosphere where charge exchange between the solar wind and interstellar neutral atoms significantly affect the physical properties of the solar wind [see Zank (2015) and references therein]. For example, non-thermal ions called pickup ions (PUIs) generated in the charge exchange process decelerate the thermal solar wind flow with a drag provided by mass loading, and PUI-driven turbulence is believed to be responsible for the steady rise in solar wind temperature beyond ∼10 AU (Matthaeus et al 1999;Isenberg et al 2003;Isenberg 2005;Smith et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Modeling the Solar Wind at the Ulysses, Voyager, and New Horizons Spacecraft

Kim

Pogorelov

Zank

et al. 2016

ApJ

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The outer heliosphere is a dynamic region shaped largely by the interaction between the solar wind and the interstellar medium. While interplanetary magnetic field and plasma observations by the Voyager spacecraft have significantly improved our understanding of this vast region, modeling the outer heliosphere still remains a challenge. We simulate the three-dimensional, time-dependent solar wind flow from 1 to 80 astronomical units (AU), where the solar wind is assumed to be supersonic, using a two-fluid model in which protons and interstellar neutral hydrogen atoms are treated as separate fluids. We use 1-day averages of the solar wind parameters from the OMNI data set as inner boundary conditions to reproduce time-dependent effects in a simplified manner which involves interpolation in both space and time. Our model generally agrees with Ulysses data in the inner heliosphere and Voyager data in the outer heliosphere. Ultimately, we present the model solar wind parameters extracted along the trajectory of New Horizons spacecraft. We compare our results with in situ plasma data taken between 11 and 33 AU and at the closest approach to Pluto on July 14, 2015.

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Faltering Steps Into the Galaxy: The Boundary Regions of the Heliosphere

Cited by 132 publications

References 212 publications

Bow shock nebulae of hot massive stars in a magnetized medium

Bow shock nebulae of hot massive stars in a magnetized medium

Heliosheath Magnetic Field and Plasma Observed by Voyager 2 During 2012 in the Rising Phase of Solar Cycle 24

Modeling the Solar Wind at the Ulysses, Voyager, and New Horizons Spacecraft

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