{
  "id": "1506.02408",
  "version": "v1",
  "published": "2015-06-08T09:19:01.000Z",
  "updated": "2015-06-08T09:19:01.000Z",
  "title": "The Temporal Behaviour of Lyman-alpha Emission During Solar Flares From SDO/EVE",
  "authors": [
    "Ryan O. Milligan",
    "Phillip C. Chamberlin"
  ],
  "comment": "Submitted to A&A Research Notes, 4 pages 4 figures",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "Despite being the most prominent emission line in the solar spectrum, there has been a notable lack of studies devoted to variations in Lyman-alpha (Ly$\\alpha$) emission during solar flares in recent years. The few examples that do exist, however, have shown Ly$\\alpha$ emission to be a substantial radiator of the total energy budget of solar flares (on the order of 10%). It is also a known driver of fluctuations in earth's ionosphere. The EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory now provides broadband, photometric Ly$\\alpha$ data at 10 s cadence, and has observed scores of solar flares in the 5 years since it was launched. However, the time profiles appear to display a rise time of tens of minutes around the time of the flare onset. This is in stark contrast to the rapid, impulsive increase observed in other intrinsically chromospheric features (H$\\alpha$, Ly$\\beta$, LyC, C III, etc.). Furthermore, the Ly$\\alpha$ emission peaks around the time of the peak of thermal soft X-ray emission, rather than during the impulsive phase when energy deposition in the chromosphere - often assumed to be in the form of nonthermal electrons - is greatest. The time derivative of Ly$\\alpha$ lightcurves also closely resembles that of the time derivative of soft X-rays, rather reminiscent of the Neupert Effect. To establish whether this atypical behaviour is a characteristic of flare heating in the lower solar atmosphere during explosive events, or a manifestation of the broadband nature of the EVE observations, comparisons have been made with spectrally-resolved Ly$\\alpha$ measurements during flares from SORCE/SOLSTICE, and other broadband photometers such as PROBA2/LYRA and GOES/EUVS-E.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-06-08T09:19:01.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "solar flares",
      "lyman-alpha emission",
      "temporal behaviour",
      "thermal soft x-ray emission",
      "total energy budget"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 4,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2015TESS....130701M"
    }
  }
}