Abstract
Abstract. The main ionization source of the middle and low Earth's atmosphere is related to energetic particles coming from outer space. Usually it is ionization from cosmic rays that is always present in the atmosphere. But in a case of a very strong solar eruption, some solar energetic particles (SEPs) can reach middle/low atmosphere increasing the ionization rate up to some orders of magnitude at polar latitudes. We continue investigating such a special class of solar events and their possible applications for natural variations of the aerosol content. After the case study of the extreme SEP event of January 2005 and its possible effect upon polar stratospheric aerosols, here we analyze atmospheric applications of the sequence of several events that took place over autumn 1989. Using aerosol data obtained over polar regions from two satellites with space-borne optical instruments SAGE II and SAM II that were operating during September–October 1989, we found that an extreme major SEP event might have led to formation of new particles and/or growth of preexisting ultrafine particles in the polar stratospheric region. However, the effect of the additional ambient air ionization on the aerosol formation is minor, in comparison with temperature effect, and can take place only in the cold polar atmospheric conditions. The extra aerosol mass formed under the temperature effect allows attributing most of the changes to the "ion–aerosol clear sky mechanism".
Highlights
solar energetic particle (SEP) event of January 2005 and its possible effect upon polar stratospheric aerosols, here we analyze atmospheric applications of the sequence of several events that took place over
October 1989, we found that an extreme major SEP event might have led to formation of new particles and/or growth cause factor tmheakceosnittemdipffiocruarltytfoEassttauedrxytphathneSsinoyanstuotrfeatlhmvearainatbhirloitpyoogfenthice of preexisting ultrafine particles in the polar stratospheric re- terrestrial system, including the sSolcariefanctcore, bsy means of stagion
We focus on short-time sporadic solar eruptive events, which can help in separating the cosmic ray effect because of its sharp temporal and spatial localization
Summary
For our analysis we have chosen the time interval of September–October 1989, where a series of major SEP events, recorded as ground level enhancements (GLEs) of ground-based neutron monitors, took place. These SEP events were among the strongest ones in the 22nd solar cycle (Duldig et al, 1993; Lovell et al, 1998). The atmospheric conditions were monitored by several spaceborne instruments during that period, making a detailed case study possible. While the chemistry of the upper atmosphere is known to be greatly affected by the SEP events in autumn of 1989 (Vitt et al, 2000; Verronen et al, 2002), a direct detailed analysis of the low and middle atmosphere data has not been done previously
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