scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
The influence of precipitating solar and magnetospheric particles on the entire
atmosphere - Simulations with HAMMONIA
Kieser Jens 1 , Schmidt Hauke 1 , Wissing Jan Maik 2 , Kallenrode May-Britt 2
1 Max Planck Institute for Meteorology, 2 University of Osnabrück
When energetic charged particles of solar and magnetospheric origin precipitate into the
Earth's atmosphere they can affect atmospheric chemistry, energy budget, and dynamics. The
occurence, composition, and energy of such precipitating energetic particles are highly
variable in time and space but crucial for the location where they deposit their energy and
initialize atmospheric processes.
To study the influence of precipitating solar and magnetospheric particles on the entire
atmosphere during the solar and magnetospheric storms in October/November 2003 and the
following months we use the 3-D chemistry and climate model HAMMONIA (Hamburg
Model of the Neutral and Ionized Atmosphere) [Schmidt et al., J. Climate, 2006]. The model
treats atmospheric dynamics, radiation, and chemistry interactively for the height range from
the Earth's surface to the thermosphere (approximately 250 km). 3-D sets of ion pair
production rates for precipitating solar and magnetospheric protons, electrons, and alphaparticles
are provided by AIMOS (Atmospheric Ionization Module Osnabrück) [Wissing and
Kallenrode, J. Geophys. Res., 2009].
Our model computations point out the substantial impact of precipitating energetic particles
on the polar middle and upper atmosphere. Simulations show significant enhancements in
middle and upper atmospheric NOx content and thermospheric ion concentrations during the
period of very intense particle storms which happened in October/November 2003.
Further, our model results indicate a noticeable influence of precipitating electrons in the
lower mesosphere during individual events. Generally, electrons play the major role in NOx
production in the auroral upper mesosphere and lower thermosphere. It can be shown that
downward transport events carry large amounts of NOx from the mesopause to the stratopause
region. This illustrates that neglecting electrons in studies of precipitating particles may lead
to a significant error in the assessment of chemical background conditions.
Besides their influence on atmospheric chemistry we also study the effects of particles on
energetics and dynamics. A temperature decrease in the sunlit middle atmosphere is
associated with a particle induced ozone depletion. In the thermosphere precipitating particles
control a couple of energy relevant processes leading, in general, to a net warming. However,
a net cooling caused by particle influence in a small altitude range in the polar summer
thermosphere can be shown.