Density of neutral interstellar hydrogen at the termination shock from Ulysses pickup ion observations

Bzowski, M.; Möbius, E.; Tarnopolski, S.; Izmodenov, Vladislav; Gloeckler, G.

doi:10.1051/0004-6361:20078810

Cited by 88 publications

(149 citation statements)

References 75 publications

(100 reference statements)

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“…The Bzowski et al 2008). The interstellar electron density in the CHISM is expected to be somewhat lower than the sightline averaged value, because of radiative transfer effects, and higher values are found towards stars sampling other parts of the CHISM (Sect.…”

Section: Circumheliospheric Interstellar Materials and The Local Intermentioning

confidence: 97%

“…The breakdown between the primary and secondary populations and exact values of their densities, bulk velocities, and temperatures depend on the conditions in the unperturbed CHISM. For example, in a recent report on the determination of the density of neutral interstellar hydrogen at the TS, Bzowski et al (2008) adopted the following parameters in the CHISM: the upwind direction λ B = 254.68 • , φ B = 5.31 • in the B1950.0 ecliptic coordinates (Witte 2004;); bulk velocity V B = 26.3 km s −1 ; temperature T B = 6400 K; density of neutral He equal to 0.015 cm −3 ; and based on the He ionization degree in the LIC inferred by Wolff et al (1999) on the level of ∼30-40%, the density of He + equal to 0.008 cm −3 , in agreement with He ionization levels predicted by radiative transfer models of the CHISM (Sect. 4.3).…”

Section: Hydrogenmentioning

confidence: 99%

“…Units of the horizontal axis are AU, the units of the vertical axis are km s −1 . The profiles were calculated using the Warsaw time-dependent kinetic model of heliospheric hydrogen (Bzowski et al 1997) with time-dependent radiation pressure and ionization rate, and assuming the boundary conditions at the termination shock according to case 2, which seem to be close to actual parameters in this region based on analysis of Ulysses pickup ion measurements by Bzowski et al (2008). The radiation pressure for 1996.0, adopted as the solar minimum case, was equal to μ = 0.9; for 1999.5, adopted as the solar maximum case, it was equal to μ = 1.4…”

Section: Hydrogenmentioning

confidence: 99%

“…2.3). The prediction of R g/d from the radiative (Gloeckler and Fisk 2007;Bzowski et al 2008; † Interstellar densities are based on radiative transfer models 14, 26-42, in Table 4 of ‡ The filtration ratio is the percentage of the neutral that survives traversal of the heliosheath regions…”

Section: Circumheliospheric Interstellar Materials and The Local Intermentioning

confidence: 99%

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The Galactic Environment of the Sun: Interstellar Material Inside and Outside of the Heliosphere

et al. 2009

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Interstellar material (ISMa) is observed both inside and outside of the heliosphere. Relating these diverse sets of ISMa data provides a richer understanding of both the interstellar medium and the heliosphere. The galactic environment of the Sun is dominated by warm, low-density, partially ionized interstellar material consisting of atoms and dust grains. The properties of the heliosphere are dependent on the pressure, composition, radiation field, ionization, and magnetic field of ambient ISMa. The very low-density interior of the Local Bubble, combined with an expanding superbubble shell associated with star formation in the Scorpius-Centaurus Association, dominate the properties of the local interstellar medium (LISM). Once the heliosphere boundaries and interaction mechanisms are understood, interstellar gas, dust, pickup ions, and anomalous cosmic rays inside of the heliosphere can be directly compared to ISMa outside of the heliosphere. Our understanding of ISMa at the Sun is further enriched when the circumheliospheric interstellar material is compared to observations of other nearby ISMa and the overall context of our galactic environment. The IBEX mission will map the interaction region between the heliosphere and ISMa, and improve the accuracy of comparisons between ISMa inside and outside the heliosphere.

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Section: Circumheliospheric Interstellar Materials and The Local Intermentioning

confidence: 97%

Section: Hydrogenmentioning

confidence: 99%

Section: Hydrogenmentioning

confidence: 99%

Section: Circumheliospheric Interstellar Materials and The Local Intermentioning

confidence: 99%

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The Galactic Environment of the Sun: Interstellar Material Inside and Outside of the Heliosphere

et al. 2009

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“…In the case of PUI protons, their production is due to photoionization and charge exchange of interstellar H-atoms (see Rucinski & Fahr 1991;Fahr & Rucinski 1999;Rucinski et al 2003;Bzowski et al 2008). Their spatial distribution seems well understood, while the PUI-phase-space transport is a much less settled subject.…”

Section: Introductionmentioning

confidence: 99%

Injection to the pick-up ion regime from high energies and induced ion power-laws

Fahr

Чашей

Verscharen

2009

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Though pick-up ions (PUIs) are a well-known phenomenon in the inner heliosphere, their phase-space distribution nevertheless is a theoretically unsettled problem. Especially the question of how PUIs form their suprathermal tails, extending to far above their injection energies, still now is unsatisfactorily answered. Though Fermi-2 velocity diffusion theories have revealed that such tails are populated, they nevertheless show that resulting population densities are much less than seen in observations showing power-laws with a velocity index of "−5". We first investigate here, whether or not observationally suggested power-laws can be the result of a quasi-equilibrium state between suprathermal ions and magnetohydrodynamic turbulences in energy exchange with each other. We demonstrate that such an equilibrium cannot be established, since it would require too high PUI pressures enforcing a shock-free deceleration of the solar wind. We furthermore show that Fermi-2 type energy diffusion in the outer heliosphere is too inefficient to determine the shape of the distribution function there. As we can show, however, power-laws beyond the injection threshold can be established, if the injection takes place at higher energies of the order of 100 keV. As we demonstrate here, such an injection is connected with modulated anomalous cosmic ray (ACR) particles at the lower end of their spectrum when they again start being convected outwards with the solar wind. Therefore, we refer to these particles as ACR-PUIs. In our quantitative calculation of the PUI spectrum resulting under such conditions we in fact find again power-laws, however with a velocity-power index of "−4" and fairly distance-independent spectral intensities. As it seems these facts are observationally well supported by VOYAGER measurements in the lowest energy channels.

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Remote diagnostic of the hydrogen wall through measurements of the backscattered solar Lyman alpha radiation by Voyager 1/UVS in 1993–2003

et al. 2016

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We perform a new analysis of the Lyman alpha data obtained by Voyager 1 during the spatial scans in 1993–2003 while Voyager 1 was at 53–88 AU from the Sun. These data are the important source of information on the hydrogen distribution in the outer heliosphere. A sophisticated global kinetic‐MHD model of the heliospheric interface and a radiative transfer model are used for the analysis. It is shown for the first time that the ratio of the Lyman alpha intensities detected in the downwind and upwind lines of sight in the outer heliosphere is sensitive to the configuration (peak value and location) of the hydrogen wall. The hydrogen wall is a source of Doppler‐shifted backscattered Lyman alpha photons, so it can be seen from inside the heliosphere. Therefore, Voyager 1/ultraviolet spectrometer (UVS) Lyman alpha data can be used for remote sensing of the hydrogen wall. We show that our current global model of the outer heliosphere, which is consistent with many other measurements including Lyman alpha data from both Voyager 1 and 2 in 1980–1993, provides a systematically larger downwind to upwind intensity ratio compared with the UVS data in 1993–2003. In order to decrease the ratio, a higher and/or closer hydrogen wall is needed.

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Density of neutral interstellar hydrogen at the termination shock from Ulysses pickup ion observations

Cited by 88 publications

References 75 publications

The Galactic Environment of the Sun: Interstellar Material Inside and Outside of the Heliosphere

The Galactic Environment of the Sun: Interstellar Material Inside and Outside of the Heliosphere

Injection to the pick-up ion regime from high energies and induced ion power-laws

Remote diagnostic of the hydrogen wall through measurements of the backscattered solar Lyman alpha radiation by Voyager 1/UVS in 1993–2003

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