The Heliosphere’s Interstellar Interaction: No Bow Shock

McComas, D. J.; Alexashov, D. B.; Bzowski, M.; Fahr, H. J.; Heerikhuisen, J.; Izmodenov, Vladislav; Lee, M. A.; Möbius, E.; Pogorelov, N. V.; Schwadron, N. A.; Zank, G. P.

doi:10.1126/science.1221054

Cited by 241 publications

(292 citation statements)

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“…These results differ significantly from the results obtained from IBEX observations by Bzowski et al (2012) and Möbius et al (2012), even after reconciling some small differences between these authors by McComas et al (2012). Both Bzowski et al (2012) and Möbius et al (2012) pointed out, however, that acceptable parameters obtained from the IBEX analysis form long narrow tubes in the parameter space.…”

Section: Resultscontrasting

confidence: 56%

“…The parameter values obtained from IBEX are tightly correlated with the inflow longitude, and the acceptable parameter ranges form long alleys in the parameter space. A follow-up IBEX analysis brought consensus values suggested by McComas et al (2012): λ = 259.0 • , β = 5.0 • (J2000), v = 23.2 km s −1 , and T = 6300 K. Based on these and other measurements from the past ∼40 years, Frisch et al (2013) suggested that the flow vector of interstellar gas in the solar neighborhood might be changing. The existence of such a trend would have profound consequences for our understanding of the physics of the heliosphere and the processes operating in the interstellar matter that surrounds the Sun.…”

Section: Motivationmentioning

confidence: 99%

“…Since the differences between the results from Ulysses and IBEX have far-reaching consequences for the physics of the heliosphere even without the variation of gas parameters in time (McComas et al 2012;Zank et al 2013), it is important to understand the reason for these differences. Another compelling question is wheter a change in time, previously not considered in the analysis, can be ruled out.…”

Section: Motivationmentioning

confidence: 99%

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Neutral interstellar He parameters in front of the heliosphere 1994–2007

Bzowski

Kubiak

Hlond

et al. 2014

A&A

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Context. A recent analysis of IBEX measurements of the neutral interstellar He flux showed that the inflow velocity vector is different from the results of an earlier analysis of observations from the GAS instrument onboard Ulysses. A recently published compilation of published results on the helium inflow direction from the past ∼40 years suggested that the inflow direction may be changing with time. Aims. We reanalyzed the old Ulysses data and reprocessed them to increase the accuracy of the instrument pointing to investigate whether the GAS/Ulysses observations, carried out during almost two solar cycles, support the hypothesis that the direction of the interstellar helium inflow is changing. Methods. We employed a similar analysis method as had been used in the analysis of the IBEX data. We sought a parameter set that minimizes the reduced χ 2 , using the Warsaw test-particle model for the interstellar He flux at Ulysses with a state-of-the-art model of neutral He ionization in the heliosphere that precisely reproduces the observation conditions. We also propose a supplementary method of constraining the parameters based on cross-correlations of parameters obtained from an analysis of carefully selected subsets of data. Results. We find that the ecliptic longitude and speed of interstellar He agree very well with the values reported in the original GAS analysis. We find, however, that the temperature is markedly higher. The three-seasons best-fit parameter set is λ = 255.3 • , β = 6 • (J2000), v = 26.0 km s −1 , and T = 7500 K. We do not find evidence that these parameters are varying with time, but their uncertainty range is wider than originally reported. Conclusions. The originally derived parameters of interstellar He from direct sampling on GAS/Ulysses agree well with those currently derived, except for the temperature, which seems to be appreciably higher; this agrees well with interstellar absorption line results. While the results of our analysis agree marginally with the previously reported results from IBEX, the most likely values from the two analyses differ for reasons that are still not understood.

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Section: Resultscontrasting

confidence: 56%

Section: Motivationmentioning

confidence: 99%

Section: Motivationmentioning

confidence: 99%

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Neutral interstellar He parameters in front of the heliosphere 1994–2007

Bzowski

Kubiak

Hlond

et al. 2014

A&A

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“…Although mass loading plays an important role in the dynamics of the solar wind (Baranov et al 1971;Baranov 1990;Zank 1999), there are a number of key differences between this scenario and the pulsar wind scenario. Firstly, the velocity of the Sun through the ISM is, most likely, weakly sub-fast magnetosonic (McComas et al 2012), whereas the pulsar's motion is highly supersonic; secondly, the pulsar wind is very light -composed of lepton pairs -and one would therefore expect mass loading to have a greater effect; thirdly, most of the research related to mass loading in the solar wind concen- trated on flow in the head region, while we are interested in the large scale dynamics of the tail flows.…”

Section: Introductionmentioning

confidence: 99%

Mass loading of bow shock pulsar wind nebulae

Morlino

Lyutikov

Vorster

2015

Mon. Not. R. Astron. Soc.

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We investigate the dynamics of bow shock nebulae created by pulsars moving supersonically through a partially ionized interstellar medium. A fraction of interstellar neutral hydrogen atoms penetrating into the tail region of a pulsar wind will undergo photo-ionization due to the UV light emitted by the nebula, with the resulting mass loading dramatically changing the flow dynamics of the light leptonic pulsar wind. Using a quasi 1-D hydrodynamic model of both non-relativistic and relativistic flow, and focusing on scales much larger than the stand-off distance, we find that if a relatively small density of neutral hydrogen, as low as 10 −4 cm −3 , penetrate inside the pulsar wind, this is sufficient to strongly affect the tail flow. Mass loading leads to the fast expansion of the pulsar wind tail, making the tail flow intrinsically non-stationary. The shapes predicted for the bow shock nebulae compare well with observations, both in Hα and X-rays.

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“…Similar to the shock wave around a supersonic aircraft, the bow shock is thought to form as the Solar System ploughs through the interstellar medium, forcing the local ionized gas to change density abruptly and discontinuously. But in May, McComas and his colleagues reported 4 that data from NASA's Interstellar Boundary Explorer (IBEX) mission cast doubt on this picture. From Earth orbit, IBEX probes the interstellar medium by detecting electrically neutral atoms that slip into the Solar System through the heliopause.…”

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confidence: 99%

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2012

Nature

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The Heliosphere’s Interstellar Interaction: No Bow Shock

Cited by 241 publications

References 35 publications

Neutral interstellar He parameters in front of the heliosphere 1994–2007

Neutral interstellar He parameters in front of the heliosphere 1994–2007

Mass loading of bow shock pulsar wind nebulae

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