ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-1979-2011 Ionization effect of solar particle GLE events in low and\ middle atmosphere Usoskin I. G. 1 Kovaltsov G. A. 2 Mironova I. A. 3 Tylka A. J. 4 Dietrich W. F. 5 Sodankylä Geophysical Observatory (Oulu unit), University of Oulu, Finland Ioffe Physical-Technical Institute, St. Petersburg, Russia Institute of Physics, St.Petersburg State University, St. Petersburg, Russia Space Science Division, Naval Research Laboratory, Washington, DC, USA Praxis, Inc., Alexandria, VA, USA 03 03 2011 11 5 1979 1988 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/11/1979/2011/acp-11-1979-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/1979/2011/acp-11-1979-2011.pdf

Using a new reconstruction of the solar proton energy spectra for Ground Level Enhancement (GLE) events, based on fits to measurements from ground-based and satellite-borne instruments covering a wide energy range, we quantitatively evaluate the possible ionization effects in the low and middle atmosphere for 58 out of the 66 GLE events recorded by the world-wide neutron monitor network since 1956. The ionization computations are based on the numerical 3D CRAC:CRII model. A table of the ionization effect caused by the GLE events at different atmospheric heights is provided. It is shown that the direct ionization effect is negligible or even negative, due to the accompanying Forbush decreases, in all low- and mid-latitude regions. The ionization effect is important only in the polar atmosphere, where it can be dramatic in the middle and upper atmosphere (above 30 km) during major GLE events.

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