EFFECTS OF ENERGETIC SOLAR PARTICLES ON OZONE AND MINOR ATMOSPHERIC COMPONENTS INSIDE THE POLAR REGIONS

INAF-IFSI, CNR-ICES

Solar activity influences the Earth’s environment, in particular the atmospheric
ozone, by the direct output of the e.m. radiation or through the variability of the
incoming cosmic ray flux (solar and galactic particles). Especially energetic particles,
arising from huge explosions on the Sun’s surface, travel in the interplanetary
medium and, if the circumstances were favorable, they could enter the terrestrial
atmosphere (driven by the geomagnetic field lines of our planet) and reach the polar
cap regions (geomagnetic latitude > 60°). There, they provide additional external
energy and are able to produce ionizations, dissociations, dissociative ionizations
and excitations phenomena by interacting with the minor constituents. The induced
changes are not confined to the ion chemistry but also to the neutral components. In
this way a rise of the concentration of HOx and NOx species and the triggering of
catalytic cycles which lead to short (hours) and medium (days) term ozone
destruction occur. Finally, also no-reactive reservoir species (e.g., HNO3, HCl, HOCl)
are involved in these processes and endure large variations.
The present thesis highlights the chemical variability of the middle atmosphere
during and after some Solar Energetic Particle (SEP) events recorded during the
current solar cycle. Special attention has been paid to the relationship between
ozone and HOx data (retrieved from the Microwave Limb Sounder of EOS AURA
satellite) for four events referred to 2005. The HOx data, recorded for the first time
during the intense ionization caused by the SEP flux, have pointed out some features
related to these phenomena not wholly captured by the current theoretical models. In
addition, they have highlighted that the HOx rise is able to destroy the so-called third
ozone peak at the polar latitudes of the winter hemisphere and it occurs also during
medium intensity events. Besides, the analyses of January 2005 SEP events have
shown that the changes on the hydrogen species leaded to variability in the
concentration and partitioning of chlorine family, not discernible in the summer
hemisphere. Further, the use of data coming from the HALOE instrument, referred to
SEP events occurred in July 2000 and April 2002, has in short confirmed past
experimental results. Finally, the study of a little SEP event occurred during May 2003
has pointed out that SEP events are not the unique ionization source inside the polar
latitudes during the winter.

Damiani A. et al., Ozone variability related to several SEP events occurring during solar cycle no. 23, Advances in Space Research, doi:10.1016/j.asr.2008.06.006, 2008

Damiani A. et al., Southern ozone variations induced by solar particle events during 15 January-5 February 2005, Journal of atmospheric and solar-terrestrial physics, 68, 2042-2052, 2006

Damiani A. et al., Solar particle effects on minor components of the Polar atmosphere, Annales Geophysicae, 26, 361-370, 2008