Parameters of the Supernova-Driven Interstellar Turbulence
Galactic dynamo models take as input certain parameters of the interstellar turbulence, most essentially the correlation time <inline-formula><math display="inline"><semantics><mi>τ</mi></semantics></math></inline-formula>, root-mean-square t...
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MDPI AG
2020-07-01
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| Series: | Galaxies |
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| Online Access: | https://www.mdpi.com/2075-4434/8/3/56 |
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| author | Luke Chamandy Anvar Shukurov |
| author_facet | Luke Chamandy Anvar Shukurov |
| author_sort | Luke Chamandy |
| collection | DOAJ |
| description | Galactic dynamo models take as input certain parameters of the interstellar turbulence, most essentially the correlation time <inline-formula><math display="inline"><semantics><mi>τ</mi></semantics></math></inline-formula>, root-mean-square turbulent speed <i>u</i>, and correlation scale <i>l</i>. However, these quantities are difficult, or, in the case of <inline-formula><math display="inline"><semantics><mi>τ</mi></semantics></math></inline-formula>, impossible, to directly observe, and theorists have mostly relied on order of magnitude estimates. Here we present an analytic model to derive these quantities in terms of a small set of more accessible parameters. In our model, turbulence is assumed to be driven concurrently by isolated supernovae (SNe) and superbubbles (SBs), but clustering of SNe to form SBs can be turned off if desired, which reduces the number of model parameters by about half. In general, we find that isolated SNe and SBs can inject comparable amounts of turbulent energy into the interstellar medium, but SBs do so less efficiently. This results in rather low overall conversion rates of SN energy into turbulent energy of ∼1–3%. The results obtained for <i>l</i>, <i>u</i> and <inline-formula><math display="inline"><semantics><mi>τ</mi></semantics></math></inline-formula> for model parameter values representative of the Solar neighbourhood are consistent with those determined from direct numerical simulations. Our analytic model can be combined with existing dynamo models to predict more directly the magnetic field properties for nearby galaxies or for statistical populations of galaxies in cosmological models. |
| first_indexed | 2024-03-10T18:04:02Z |
| format | Article |
| id | doaj.art-474365fe5efd46c5b12b954829da6773 |
| institution | Directory Open Access Journal |
| issn | 2075-4434 |
| language | English |
| last_indexed | 2024-03-10T18:04:02Z |
| publishDate | 2020-07-01 |
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| series | Galaxies |
| spelling | doaj.art-474365fe5efd46c5b12b954829da67732023-11-20T08:38:33ZengMDPI AGGalaxies2075-44342020-07-01835610.3390/galaxies8030056Parameters of the Supernova-Driven Interstellar TurbulenceLuke Chamandy0Anvar Shukurov1Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USASchool of Mathematics, Statistics & Physics, Newcastle University, Newcastle upon Tyne NE1 7RU, UKGalactic dynamo models take as input certain parameters of the interstellar turbulence, most essentially the correlation time <inline-formula><math display="inline"><semantics><mi>τ</mi></semantics></math></inline-formula>, root-mean-square turbulent speed <i>u</i>, and correlation scale <i>l</i>. However, these quantities are difficult, or, in the case of <inline-formula><math display="inline"><semantics><mi>τ</mi></semantics></math></inline-formula>, impossible, to directly observe, and theorists have mostly relied on order of magnitude estimates. Here we present an analytic model to derive these quantities in terms of a small set of more accessible parameters. In our model, turbulence is assumed to be driven concurrently by isolated supernovae (SNe) and superbubbles (SBs), but clustering of SNe to form SBs can be turned off if desired, which reduces the number of model parameters by about half. In general, we find that isolated SNe and SBs can inject comparable amounts of turbulent energy into the interstellar medium, but SBs do so less efficiently. This results in rather low overall conversion rates of SN energy into turbulent energy of ∼1–3%. The results obtained for <i>l</i>, <i>u</i> and <inline-formula><math display="inline"><semantics><mi>τ</mi></semantics></math></inline-formula> for model parameter values representative of the Solar neighbourhood are consistent with those determined from direct numerical simulations. Our analytic model can be combined with existing dynamo models to predict more directly the magnetic field properties for nearby galaxies or for statistical populations of galaxies in cosmological models.https://www.mdpi.com/2075-4434/8/3/56turbulencegalaxies: ISMISM: kinematics and dynamicsdynamogalaxies: spiralgalaxies: magnetic fields |
| spellingShingle | Luke Chamandy Anvar Shukurov Parameters of the Supernova-Driven Interstellar Turbulence Galaxies turbulence galaxies: ISM ISM: kinematics and dynamics dynamo galaxies: spiral galaxies: magnetic fields |
| title | Parameters of the Supernova-Driven Interstellar Turbulence |
| title_full | Parameters of the Supernova-Driven Interstellar Turbulence |
| title_fullStr | Parameters of the Supernova-Driven Interstellar Turbulence |
| title_full_unstemmed | Parameters of the Supernova-Driven Interstellar Turbulence |
| title_short | Parameters of the Supernova-Driven Interstellar Turbulence |
| title_sort | parameters of the supernova driven interstellar turbulence |
| topic | turbulence galaxies: ISM ISM: kinematics and dynamics dynamo galaxies: spiral galaxies: magnetic fields |
| url | https://www.mdpi.com/2075-4434/8/3/56 |
| work_keys_str_mv | AT lukechamandy parametersofthesupernovadriveninterstellarturbulence AT anvarshukurov parametersofthesupernovadriveninterstellarturbulence |