Parameters of the Supernova-Driven Interstellar Turbulence

Chamandy, Luke; Shukurov, Anvar

doi:10.3390/galaxies8030056

Cited by 16 publications

(14 citation statements)

References 89 publications

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“…This is consistent with an application of the test-field method (Bendre 2018) and yields rms values for α in Models L2, H2 and L2-cl of 15, 30, and 89 km s −1 , which correspond reasonably to calculations of u ′ included in Figure 11(c). It is slightly higher than the 5 Myr determined by Hollins et al (2017), the 1.9 Myr of Brandenburg et al (2013), or the order of magnitude estimate 3-7 Myr of (Chamandy & Shukurov 2020). Whether τ differs between magnetic and kinetic α, or overall, a factor of 1/5 would not qualitatively alter the dynamics.…”

Section: The α-Effectmentioning

confidence: 68%

The Small-scale Dynamo in a Multiphase Supernova-driven Medium

Gent

Low

Käpylä

et al. 2023

ApJ

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Magnetic fields grow quickly, even at early cosmological times, suggesting the action of a small-scale dynamo (SSD) in the interstellar medium (ISM) of galaxies. Many studies have focused on idealized, isotropic, homogeneous, turbulent driving of the SSD. Here we analyze more realistic simulations of supernova-driven turbulence to understand how it drives an SSD. We find that SSD growth rates are intermittently variable as a result of the evolving multiphase ISM structure. Rapid growth in the magnetic field typically occurs in hot gas, with the highest overall growth rates occurring when the fractional volume of hot gas is large. SSD growth rates correlate most strongly with vorticity and fluid Reynolds number, which also both correlate strongly with gas temperature. Rotational energy exceeds irrotational energy in all phases, but particularly in the hot phase while SSD growth is most rapid. Supernova rate does not significantly affect the ISM average kinetic energy density. Rather, higher temperatures associated with high supernova rates tend to increase SSD growth rates. SSD saturates with total magnetic energy density around 5% of equipartition to kinetic energy density, increasing slightly with magnetic Prandtl number. While magnetic energy density in the hot gas can exceed that of the other phases when SSD grows most rapidly, it saturates below 5% of equipartition with kinetic energy in the hot gas, while in the cold gas it attains 100%. Fast, intermittent growth of the magnetic field appears to be a characteristic behavior of supernova-driven, multiphase turbulence.

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Section: The α-Effectmentioning

confidence: 68%

The Small-scale Dynamo in a Multiphase Supernova-driven Medium

Gent

Low

Käpylä

et al. 2023

ApJ

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“…This is consistent with an application of the test-field method (Bendre 2018) and yields rms values for α in Models L2, H2, and L2-cl of 15, 30, and 89 kms −1 , which correspond reasonably to calculations of ¢ u included in Figure 7(c). This value of τ is slightly higher than the 5 Myr determined by Hollins et al (2017), the 1.9 Myr of Brandenburg et al (2013), or the order of magnitude estimate of 3-7 Myr of Chamandy & Shukurov (2020). Whether τ differs between magnetic and kinetic α, or overall, a factor of 1/5 would not qualitatively alter the dynamics.…”

Section: The α-Effectmentioning

confidence: 61%

Transition from Small-scale to Large-scale Dynamo in a Supernova-driven, Multiphase Medium

Gent,

Mac Low,

Korpi-Lagg

2024

ApJ

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Magnetic fields are now widely recognized as critical at many scales to galactic dynamics and structure, including multiphase pressure balance, dust processing, and star formation. Using imposed magnetic fields cannot reliably model the interstellar medium's (ISM) dynamical structure nor phase interactions. Dynamos must be modeled. ISM models exist of turbulent magnetic fields using small-scale dynamo (SSD). Others model the large-scale dynamo (LSD) organizing magnetic fields at the scale of the disk or spiral arms. Separately, neither can fully describe the galactic magnetic field dynamics nor topology. We model the LSD and SSD together at a sufficient resolution to use the low explicit Lagrangian resistivity required. The galactic SSD saturates within 20 Myr. We show that the SSD is quite insensitive to the presence of an LSD and is even stronger in the presence of a large-scale shear flow. The LSD grows more slowly in the presence of SSD, saturating after 5 Gyr versus 1–2 Gyr in studies where the SSD is weak or absent. The LSD primarily grows in warm gas in the galactic midplane. Saturation of the LSD occurs due to α-quenching near the midplane as the growing mean-field produces a magnetic α that opposes the kinetic α. The magnetic energy in our models of the LSD shows a slightly sublinear response to increasing resolution, indicating that we are converging toward the physical solution at 1 pc resolution. Clustering supernovae in OB associations increases the growth rates for both the SSD and the LSD, compared to a horizontally uniform supernova distribution.

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“…where r is the initial separation between a pair of stars, and v is the absolute value of their initial velocity difference. The injected turbulent speed V L and the injection scale L have typical values as ∼10 km s −1 and ∼100 pc for interstellar turbulence (Chamandy & Shukurov 2020). The power-law index α reflects the properties of turbulence, which is typically 1/3 for solenoidal turbulent motions with the Kolmogorov scaling, and close to 1/2 for highly compressive turbulent motions dominated by shocks (Federrath et al 2009;Kowal & Lazarian 2010).…”

Section: Initial Turbulent Velocities Of Interstellar Gas and Starsmentioning

confidence: 99%

Wide-binary Stars Formed in the Turbulent Interstellar Medium

Hwang

Hamilton

Lai

2023

ApJL

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The ubiquitous interstellar turbulence regulates star formation and the scaling relations between the initial velocity differences and the initial separations of stars. We propose that the formation of wide binaries with initial separations r in the range ∼103 au ≲ r ≲ 105 au is a natural consequence of star formation in the turbulent interstellar medium. With the decrease of r, the mean turbulent relative velocity v tur between a pair of stars decreases, while the largest velocity v bon at which they still may be gravitationally bound increases. When v tur < v bon, a wide binary can form. In this formation scenario, we derive the eccentricity distribution p(e) of wide binaries for an arbitrary relative velocity distribution. By adopting a turbulent velocity distribution, we find that wide binaries at a given initial separation generally exhibit a superthermal p(e), irrespective of the exact turbulent velocity scaling. This provides a natural explanation for the observed superthermal p(e) of the wide binaries in the solar neighborhood.

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Parameters of the Supernova-Driven Interstellar Turbulence

Cited by 16 publications

References 89 publications

The Small-scale Dynamo in a Multiphase Supernova-driven Medium

The Small-scale Dynamo in a Multiphase Supernova-driven Medium

Transition from Small-scale to Large-scale Dynamo in a Supernova-driven, Multiphase Medium

Wide-binary Stars Formed in the Turbulent Interstellar Medium

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