{
  "id": "2207.12894",
  "version": "v1",
  "published": "2022-07-21T16:52:58.000Z",
  "updated": "2022-07-21T16:52:58.000Z",
  "title": "Interface Region Imaging Spectrograph (IRIS) Observations of the Fractal Dimension in the Solar Atmosphere",
  "authors": [
    "Markus J. Aschwanden",
    "Nived Vilangot Nhalil"
  ],
  "comment": "14 pages text, 3 Tables, 5 Figures",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "While previous work explored the fractality and self-organized criticality (SOC) of flares and nanoflares in wavelengths emitted in the solar corona (such as in hard X-rays, soft X-rays, and EUV wavelenghts), we focus here on impulsive phenomena in the photosphere and transition region, as observed with the {\\sl Interface Region Imaging Spectrograph (IRIS)} in the temperature range of $T_e \\approx 10^4-10^6$ K. We find the following fractal dimensions (in increasing order): $D_A=1.21 \\pm 0.07$ for photospheric granulation, $D_A=1.29 \\pm 0.15$ for plages in the transition region, $D_A=1.54 \\pm 0.16$ for sunspots in the transition region, $D_A=1.59 \\pm 0.08$ for magnetograms in active regions, $D_A=1.56 \\pm 0.08$ for EUV nanoflares, $D_A=1.76 \\pm 0.14$ for large solar flares, and up to $D_A=1.89 \\pm 0.05$ for the largest X-class flares. We interpret low values of the fractal dimension ($1.0 \\lapprox D_A \\lapprox 1.5$) in terms of sparse curvi-linear flow patterns, while high values of the fractal dimension ($1.5 \\lapprox D_A \\lapprox 2.0$) indicate near space-filling transport processes, such as chromospheric evaporation. Phenomena in the solar transition region appear to be consistent with SOC models, based on their size distributions of fractal areas $A$ and (radiative) energies $E$, which show power law slopes of $\\alpha_A^{obs}=2.51 \\pm 0.21$ (with $\\alpha_A^{theo}=2.33$ predicted), and $\\alpha_E^{obs}=2.03 \\pm 0.18$ (with $\\alpha_E^{theo}=1.80$ predicted).",
  "revisions": [
    {
      "version": "v1",
      "updated": "2022-07-21T16:52:58.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "interface region imaging spectrograph",
      "fractal dimension",
      "solar atmosphere",
      "observations",
      "sparse curvi-linear flow patterns"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 14,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}