Could the Local Cavity be an Irregularly Shaped Strömgren Sphere?*

Linsky, Jeffrey L.; Redfield, Seth

doi:10.3847/1538-4357/ac1feb

Cited by 16 publications

(16 citation statements)

References 78 publications

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“…The structure and distribution of truly Local Interstellar Clouds is also relevant. Linsky et al (2019) and Linsky & Redfield (2021) find partially ionized clouds on the scale of parsecs.…”

Section: The Galactic Distribution Of Plasma Scatteringmentioning

confidence: 99%

A Scintillation Arc Survey of 22 Pulsars with Low to Moderate Dispersion Measures

Stinebring

Rickett

Minter³

et al. 2022

ApJ

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Context. By providing information about the location of scattering material along the line of sight (LoS) to pulsars, scintillation arcs are a powerful tool for exploring the distribution of ionized material in the interstellar medium (ISM). Here, we present observations that probe the ionized ISM on scales of ∼0.001–30 au. Aims. We have surveyed pulsars for scintillation arcs in a relatively unbiased sample with DM < 100 pc cm−3. We present multifrequency observations of 22 low to moderate DM pulsars. Many of the 54 observations were also observed at another frequency within a few days. Methods. For all observations, we present dynamic spectra, autocorrelation functions, and secondary spectra. We analyze these data products to obtain scintillation bandwidths, pulse broadening times, and arc curvatures. Results. We detect definite or probable scintillation arcs in 19 of the 22 pulsars and 34 of the 54 observations, showing that scintillation arcs are a prevalent phenomenon. The arcs are better defined in low DM pulsars. We show that well-defined arcs do not directly imply anisotropy of scattering. Only the presence of reverse arclets and a deep valley along the delay axis, which occurs in about 20% of the pulsars in the sample, indicates substantial anisotropy of scattering. Conclusions. The survey demonstrates substantial patchiness of the ionized ISM on both astronomical-unit-size scales transverse to the LoS and on ∼100 pc scales along it. We see little evidence for distributed scattering along most lines of sight in the survey.

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“…The structure and distribution of truly Local Interstellar Clouds is also relevant. Linsky et al (2019) and Linsky & Redfield (2021) find partially ionized clouds on the scale of parsecs.…”

Section: The Galactic Distribution Of Plasma Scatteringmentioning

confidence: 99%

A Scintillation Arc Survey of 22 Pulsars with Low to Moderate Dispersion Measures

Stinebring

Rickett

Minter³

et al. 2022

ApJ

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“…The absence of heating by pickup ion reactions results in adiabatic expansion and resulting cooling of the solar wind inside of the termination shock and then a steep jump in temperature into the million degree heliosheath. If, instead, the inter-cloud medium is similar to the warm ( ) photo-ionized Local Cavity as described by Linsky and Redfield ( 2021 ), then the heliosphere would likely be similar to the hot environment model, except that the plasma in the heliosheath and beyond the heliopause would be relatively cool in the absence of charge exchange reactions and hot inflowing plasma. For a future heliosphere embedded in a hot inter-cloud medium, will be much larger than for the LIC, but would be smaller because the completely ionized hydrogen would be deflected around the distant heliopause departing little momentum to the heliosphere.…”

Section: What Would Happen To the Heliosphere If/when It Enters The I...mentioning

confidence: 97%

Inhomogeneity in the Local ISM and Its Relation to the Heliosphere

et al. 2022

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This paper reviews past research and new studies underway of the local interstellar environment and its changing influence on the heliosphere. The size, shape, and physical properties of the heliosphere outside of the heliopause are determined by the surrounding environment – now the outer region of the Local Interstellar Cloud (LIC). The temperature, turbulence, and velocity vector of neutral atoms and ions in the LIC and other partially ionized interstellar clouds are measured from high-resolution spectra of interstellar absorption lines observed with the STIS instrument on the HST. Analysis of such spectra led to a kinematic model with many interstellar clouds defined by velocity vectors derived from radial velocity measurements. This analysis identified fifteen clouds located within about 10 pc of the Sun and their mean temperatures, turbulence, and velocity vectors. With the increasing number of sight lines now being analyzed, we find that temperatures and turbulent velocities have spatial variations within the LIC and other nearby clouds much larger than measurement uncertainties, and that these spatial variations appear to be randomly distributed and can be fit by Gaussians. The inhomogeneous length scale is less than 4,000 AU, a distance that the heliosphere will traverse in less than 600 years. The temperatures and turbulent velocities do not show significant trends with stellar distance or angle from the LIC center. If/when the Sun enters an inter-cloud medium, the physical properties of the future heliosphere will be very different from the present. For the heliosheath and the very local interstellar medium (VLISM) just outside of the heliopause, the total pressures are approximately equal to the gravitational pressure of overlying material in the Galaxy. The internal pressure in the LIC is far below that in the VLISM, but there is an uncertain ram pressure term produced by the flow of the LIC with respect to its environment.

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“…For the low density observed in the Local Bubble, this model predicts that the temperature post-shock will remain over 10 6 K for 100 pc, the approximate size of the Local Bubble. In the past, it was accepted that Local Bubble consisted of a large hot component with T ∼ 10 6 K, though such assumptions have recently been challenged (Welsh & Shelton 2009;Linsky & Redfield 2021). Despite the hot environment of supernova remnants, the quick formation of dust and even molecules in SN 1987A (Matsuura et al 2017) suggest that some component of the remnant may be neutral.…”

Section: Supernova Blast Initializationmentioning

confidence: 99%

Heliospheric Compression due to Recent Nearby Supernova Explosions

Miller,

Fields

2022

Preprint

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The widespread detection of 60 Fe in geological and lunar archives provides compelling evidence for recent nearby supernova explosions within ∼ 100 pc around 3 Myr and 7 Myr ago. The blasts from these explosions had a profound effect on the heliosphere. We perform new calculations to study the compression of the heliosphere due to a supernova blast. Assuming a steady but non-isotropic solar wind, we explore a range of properties appropriate for supernova distances inspired by recent 60 Fe data, and for a 20 pc supernova proposed to account for mass extinctions at the end-Devonian period. We examine the locations of the termination shock decelerating the solar wind and the heliopause that marks the boundary between the solar wind and supernova material. Pressure balance scaling holds, consistent with studies of other astrospheres. Solar wind anisotropy does not have an appreciable effect on shock geometry. We find that supernova explosions at 50 pc (95 pc) lead to heliopause locations at 16 au (23 au) when the forward shock arrives. Thus, the outer solar system was directly exposed to the blast, but the inner planets-including the Earth-were not. This finding reaffirms that the delivery of supernova material to the Earth is not from the blast plasma itself, but likely is from supernova dust grains. After the arrival of the forward shock, the weakening supernova blast will lead to a gradual rebound of the heliosphere, taking ∼ 100s of kyr to expand beyond 100 au. Prospects for future work are discussed.

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Could the Local Cavity be an Irregularly Shaped Strömgren Sphere?*

Cited by 16 publications

References 78 publications

A Scintillation Arc Survey of 22 Pulsars with Low to Moderate Dispersion Measures

A Scintillation Arc Survey of 22 Pulsars with Low to Moderate Dispersion Measures

Inhomogeneity in the Local ISM and Its Relation to the Heliosphere

Heliospheric Compression due to Recent Nearby Supernova Explosions

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