Encyclopedia of Natural Hazards

2013 Edition
| Editors: Peter T. Bobrowsky

Solar Flares

  • David H. BotelerEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-1-4020-4399-4_327


Solar flares are a burst of electromagnetic radiation from the Sun.


The first flare was observed in 1859 when Richard Carrington, while making sunspot drawings, saw a sudden brightening. Now, with modern instruments, we know that the burst of radiation from a solar flare lasts from a few minutes to several hours and spans the entire electromagnetic spectrum. The intensity of a flare is classified according to the X-ray flux, F, in the 0.1–0.8-nm [1–8 Å] wavelength range measured on the GOES satellite (see Table  1). The size of a flare is given by the flux value, using the classification letter as a multiplier: For example, a X4.5 flare has a peak flux of 4.5 × 10 −4 W m −2.
Solar Flares, Table 1

Solar flare classification


X-ray flux (W.m−2)


F 10−4


10−5 F > 10−4


10−6 F > 10−5

This is a preview of subscription content, log in to check access.


  1. Carrington, R. C., 1859. Description of a singular appearance seen on the Sun on September 1, 1859. Monthly Notices of the Royal Astronomical Society, 20, 13–15.CrossRefGoogle Scholar
  2. Tandberg-Hanssen, E., and Emslie, A. G., 2009. The Physics of Solar Flares. Cambridge: Cambridge University Press, p. 288.Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  1. 1.Geomagnetic LaboratoryEarth Science Sector, Natural Resources CanadaOttawaCanada