{
  "id": "2410.22408",
  "version": "v1",
  "published": "2024-10-29T18:00:02.000Z",
  "updated": "2024-10-29T18:00:02.000Z",
  "title": "Understanding Density Fluctuations in Supersonic, Isothermal Turbulence",
  "authors": [
    "Evan Scannapieco",
    "Liubin Pan",
    "Edward Buie II",
    "Marcus Brüggen"
  ],
  "comment": "40 pages, 10 figures, to appear in Science Advances",
  "categories": [
    "astro-ph.GA",
    "physics.flu-dyn"
  ],
  "abstract": "Supersonic turbulence occurs in many environments, particularly in astrophysics. In the crucial case of isothermal turbulence, the probability density function (PDF) of the logarithmic density, $s$, is well measured, but a theoretical understanding of the processes leading to this distribution remains elusive. We investigate these processes using Lagrangian tracer particles to track $s$ and $\\frac{ds}{dt}$ in direct numerical simulations, and we show that their evolution can be modeled as a stochastic differential process with time-correlated noise. The temporal correlation functions of $s$ and $\\frac{ds}{dt}$ decay exponentially, as predicted by the model, and the decay timescale is $\\approx$ 1/6 the eddy turnover time. The behavior of the conditional averages of $\\frac{ds}{dt}$ and $\\frac{d^2s}{dt^2}$ is also well explained by the model, which shows that the density PDF arises from a balance between stochastic compressions/expansions, which tend to broaden the PDF, and the acceleration/deceleration of shocks by density gradients, which tends to narrow it.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-10-29T18:00:02.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "understanding density fluctuations",
      "isothermal turbulence",
      "probability density function",
      "lagrangian tracer particles",
      "supersonic turbulence occurs"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 40,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}