{
  "id": "2009.06158",
  "version": "v1",
  "published": "2020-09-14T02:48:39.000Z",
  "updated": "2020-09-14T02:48:39.000Z",
  "title": "Spectroscopic Observations of High-speed Downflows in a C1.7 Solar Flare",
  "authors": [
    "Yi-An Zhou",
    "Y. Li",
    "M. D. Ding",
    "Jie Hong",
    "Ke Yu"
  ],
  "comment": "20 pages, 9 figures. Accepted for publication in ApJ",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "In this paper, we analyze the high-resolution UV spectra for a C1.7 solar flare (SOL2017-09-09T06:51) observed by the \\textit{Interface Region Imaging Spectrograph} (\\textit{IRIS}). {We focus on the spectroscopic observations at the locations where the cool lines of \\ion{Si}{4} 1402.8 \\AA\\ ($\\sim$10$^{4.8}$ K) and \\ion{C}{2} 1334.5/1335.7 \\AA\\ ($\\sim$10$^{4.4}$ K) reveal significant redshifts with Doppler velocities up to $\\sim$150 km s$^{-1}$.} These redshifts appear in the rise phase of the flare, then increase rapidly, reach the maximum in a few minutes, and proceed into the decay phase. Combining the images from \\textit{IRIS} and Atmospheric Imaging Assembly (AIA) on board the {\\em Solar Dynamics Observatory} ({\\em SDO}), we propose that the redshifts in the cool lines are caused by the downflows in the transition region and upper chromospheric layers, which likely result from a magnetic reconnection leading to the flare. In addition, the cool \\ion{Si}{4} and \\ion{C}{2} lines show gentle redshifts (a few tens of km s$^{-1}$) at some other locations, which manifest some distinct features from the above locations. This is supposed to originate from a different physical process.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-09-14T02:48:39.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "spectroscopic observations",
      "solar flare",
      "high-speed downflows",
      "cool lines",
      "high-resolution uv spectra"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 20,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}