Cosmic rays and total ozone at higher middle latitudes

Various external factors of solar origin like solar activity (solar cycle, 27-day variation etc.), geomagnetic storms and other solar wind-related phenomena, and changes of fluxes of high-energy particles can potentially affect the ozone layer. Here we examine the effects of Forbush decreases and other decreases of the galactic cosmic ray (GCR) flux on the columnar ozone content (= total ozone) at higher middle latitudes near 50degreesN. The Forbush decreases usually occur together with geomagnetic storms and relatively often together with solar proton events (SPEs). Then it is difficult, if not impossible, to distinguish between the effects of geomagnetic storms, SPEs and Forbush decreases and other decreases of the GCR flux. Therefore we present here the results of investigations of the effects of Forbush decreases and other substantial decreases of the GCR flux on the total ozone for events when there was no geomagnetic storm. Due to the dominance of summertime events in the selected data set, very weak if any effect is found. There is evidently no effect in zonal mean values of total ozone. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.