The Density Distribution of Compressively Forced, Supersonic Turbulence Depends on the Driving Correlation Time
Supersonic turbulence plays a critical role in shaping astrophysical systems, from molecular clouds to the circumgalactic medium. Key properties of this turbulence include the Mach number, driving scale, and nature of the driving mechanism, which can be solenoidal (divergence-free), compressive (cur...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/add936 |
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| author | Philipp Grete Evan Scannapieco Marcus Brüggen Liubin Pan |
| author_facet | Philipp Grete Evan Scannapieco Marcus Brüggen Liubin Pan |
| author_sort | Philipp Grete |
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| description | Supersonic turbulence plays a critical role in shaping astrophysical systems, from molecular clouds to the circumgalactic medium. Key properties of this turbulence include the Mach number, driving scale, and nature of the driving mechanism, which can be solenoidal (divergence-free), compressive (curl-free), or a mix of the two. A less studied property is the correlation time of the driving accelerations, τ _a . While this timescale has a minimal impact on solenoidally driven turbulence, we show that it has a strong impact on compressively driven turbulence. Using high-resolution simulations with tracer particles, we analyze the evolution of density fluctuations, focusing on the probability distribution function of the logarithmic density, s , and its rate of change, $\frac{ds}{dt},$ and the conditional statistics of $\frac{ds}{dt}$ and $\frac{{d}^{2}s}{d{t}^{2}}$ . When the driving correlation time is comparable to the eddy turnover time, τ _a ≈ τ _e , compressive driving leads to the formation of large, low-density voids in which the variance of $\frac{ds}{dt}$ is large. These are directly linked to sustained accelerated expansions, which result in a strong correlation between density and the divergence of the driving acceleration field. In contrast, when τ _a ≈ 0.1 τ _e , compressive driving does not produce such voids, resulting in a narrower, less skewed distribution. We show using analytical estimates that τ _a may be significantly less than τ _e in supernova-driven turbulence, highlighting the need to better understand the role of the driving correlation time in shaping the density structure of turbulent astrophysical systems. |
| format | Article |
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| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-d2a7dad5910248cdb494305b8a32b5ef2025-08-20T03:29:13ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01987212210.3847/1538-4357/add936The Density Distribution of Compressively Forced, Supersonic Turbulence Depends on the Driving Correlation TimePhilipp Grete0https://orcid.org/0000-0003-3555-9886Evan Scannapieco1https://orcid.org/0000-0002-3193-1196Marcus Brüggen2https://orcid.org/0000-0002-3369-7735Liubin Pan3https://orcid.org/0000-0002-0502-8593University of Hamburg , Hamburger Sternwarte, Gojenbergsweg 112, 21029, Hamburg, GermanySchool of Earth & Space Exploration, Arizona State University , 781 Terrace Mall, Tempe, AZ 85287, USA ; evan.scannapieco@asu.eduUniversity of Hamburg , Hamburger Sternwarte, Gojenbergsweg 112, 21029, Hamburg, GermanySchool of Physics and Astronomy, Sun Yat-sen University , 2 Daxue Road, Zhuhai, Guangdong, 519082, People’s Republic of China ; panlb5@mail.sysu.edu.cnSupersonic turbulence plays a critical role in shaping astrophysical systems, from molecular clouds to the circumgalactic medium. Key properties of this turbulence include the Mach number, driving scale, and nature of the driving mechanism, which can be solenoidal (divergence-free), compressive (curl-free), or a mix of the two. A less studied property is the correlation time of the driving accelerations, τ _a . While this timescale has a minimal impact on solenoidally driven turbulence, we show that it has a strong impact on compressively driven turbulence. Using high-resolution simulations with tracer particles, we analyze the evolution of density fluctuations, focusing on the probability distribution function of the logarithmic density, s , and its rate of change, $\frac{ds}{dt},$ and the conditional statistics of $\frac{ds}{dt}$ and $\frac{{d}^{2}s}{d{t}^{2}}$ . When the driving correlation time is comparable to the eddy turnover time, τ _a ≈ τ _e , compressive driving leads to the formation of large, low-density voids in which the variance of $\frac{ds}{dt}$ is large. These are directly linked to sustained accelerated expansions, which result in a strong correlation between density and the divergence of the driving acceleration field. In contrast, when τ _a ≈ 0.1 τ _e , compressive driving does not produce such voids, resulting in a narrower, less skewed distribution. We show using analytical estimates that τ _a may be significantly less than τ _e in supernova-driven turbulence, highlighting the need to better understand the role of the driving correlation time in shaping the density structure of turbulent astrophysical systems.https://doi.org/10.3847/1538-4357/add936Interplanetary turbulenceInterstellar medium |
| spellingShingle | Philipp Grete Evan Scannapieco Marcus Brüggen Liubin Pan The Density Distribution of Compressively Forced, Supersonic Turbulence Depends on the Driving Correlation Time The Astrophysical Journal Interplanetary turbulence Interstellar medium |
| title | The Density Distribution of Compressively Forced, Supersonic Turbulence Depends on the Driving Correlation Time |
| title_full | The Density Distribution of Compressively Forced, Supersonic Turbulence Depends on the Driving Correlation Time |
| title_fullStr | The Density Distribution of Compressively Forced, Supersonic Turbulence Depends on the Driving Correlation Time |
| title_full_unstemmed | The Density Distribution of Compressively Forced, Supersonic Turbulence Depends on the Driving Correlation Time |
| title_short | The Density Distribution of Compressively Forced, Supersonic Turbulence Depends on the Driving Correlation Time |
| title_sort | density distribution of compressively forced supersonic turbulence depends on the driving correlation time |
| topic | Interplanetary turbulence Interstellar medium |
| url | https://doi.org/10.3847/1538-4357/add936 |
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