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Ann. Geophys., 24, 2403-2412, 2006
www.ann-geophys.net/24/2403/2006/
© European Geosciences Union 2006
3-D GCM modelling of thermospheric nitric oxide during the 2003 Halloween storm
A. L. Dobbin, E. M. Griffin, A. D. Aylward, and G. H. Millward
Atmospheric Physics Laboratory, Department of Physics and Astronomy, University College London, Gower street, London, WC1E 6BT, UK
Abstract. Numerical modelling of thermospheric temperature changes associated with
periods of high geomagnetic activity are often inaccurate due to unrealistic
representation of nitric oxide (NO) densities and associated 5.3-μm
radiative cooling. In previous modelling studies, simplistic
parameterisations of NO density and variability have often been implemented
in order to constrain thermospheric temperature predictions and post storm
recovery timescales during and following periods of high auroral activity.
In this paper we use the University College London (UCL) 3-D Coupled
Thermosphere and Middle Atmosphere (CMAT) General Circulation Model to
simulate the 11-day period from 23 October to 3 November 2003, during which the Earth experienced some of the largest
geomagnetic activity ever recorded; the so called "Halloween
storm". This model has recently been updated to include a detailed
self consistent calculation of NO production and transport.
Temperatures predicted by the model compare well with those observed by
the UCL Fabry Perot Interferometer at Kiruna, northern Sweden, when changes
in solar and auroral activity are taken into account in the calculation of
NO densities. The spatial distribution of predicted temperatures at
approximately 250-km altitude is also discussed. Simulated NO densities at
approximately 110 km are presented. Large quantities of NO are found to be
present at to the equator, one to two days after the most intense period of
geomagnetic activity. This is the first 3-D GCM simulation of NO production
and transport over the 2003 Halloween storm period.
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