{
  "id": "2106.04220",
  "version": "v1",
  "published": "2021-06-08T10:01:13.000Z",
  "updated": "2021-06-08T10:01:13.000Z",
  "title": "ALMA observations of the variability of the quiet Sun at millimeter wavelengths",
  "authors": [
    "A. Nindos",
    "S. Patsourakos",
    "C. E. Alissandrakis",
    "T. S. Bastian"
  ],
  "comment": "A&A, accepted for publication (abbreviated abstract)",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "Using Atacama Large Millimeter/submillimeter Array (ALMA) observations of the quiet Sun at 1.26 and 3 mm, we study spatially resolved oscillations and transient brightenings, i.e. small, weak events of energy release. Both phenomena may have a bearing on the heating of the chromosphere. At 1.26 mm, in addition to power spectra of the original data, we degraded the images to the spatial resolution of the 3 mm images and used fields of view of equal area for both data sets. The detection of transient brightenings was made after the oscillations were removed. At both frequencies we detected p-mode oscillations in the range 3.6-4.4 mHz. In the corrected data sets, the oscillations at 1.26 and 3 mm showed brightness temperature fluctuations of ~1.7-1.8% with respect to the average quiet Sun, corresponding to 137 and 107 K, respectively. They represented a fraction of 0.55-0.68 of the full power spectrum and their energy density at 1.26 mm was 0.03 erg cm$^{-3}$. We detected 77 transient brightenings at 1.26 mm and 115 at 3 mm. Although the majority of the 1.26 mm events occurred in cell interior, their occurrence rate per unit area was higher than that of the 3 mm events. The computed low-end energy of the 1.26 mm transient brightenings ($1.8 \\times 10^{23}$ erg) is among the smallest ever reported, irrespective of the wavelength of observation. However, their power per unit area is smaller than that of the 3 mm events, probably due to the detection of many weak 1.26 mm events. We also found that ALMA bright network structures corresponded to dark mottles/spicules seen in broadband H$\\alpha$ images from the GONG network.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2021-06-08T10:01:13.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "quiet sun",
      "millimeter wavelengths",
      "transient brightenings",
      "mm events",
      "alma observations"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}