Ion-Chemistry in the D and E Regions from the Sodankylä
Model and EISCAT, IRIS and Satellite Observations
C F del Pozo1,
I W McCrea2,
E Turunen3, Th Ulich3,
J K Hargreaves4
1Dept. of Physics, University of Wales at Aberystwyth,
2EISCAT Group, Rutherford Appleton Laboratory, Didcot, U.K.
3Geophysical Observatory, FIN-99600 Sodankylä,
4Engineering Department, Lancaster University, U.K.
We apply the Sodankylä chemical model to the analysis of EISCAT
observations of the D and E regions. The model is extended to the
study of the auroral region by estimating the precipitation production
function - and the particle spectrum - from the 'inversion' of the raw
density profiles measured by the radars. During some periods, the
precipitation fluxes measured by the DMSP and SAMPEX satellites are
compared with the model estimates. Imaging riometer (IRIS)
observations, on the other hand, are used to define the space-time
extent and uniformity of the precipitation region, and to better
qualify the satellite conjunction.
Typically, the VHF radar measures the ion-line at heights between 75
and 105 km which covers the lower E-region and the upper D-region
dominated by the cluster and hydated ions. The UHF radar looks at
heights below 85 km, down to 55 km or so, when the background density
is greater than 109 m-3, particularly during PCA
events. Below 75 km the negative ions are dominant and the width of
the ion-line is proportional to the total negative ion
concentration. The raw densities are used as input to the
Sodankylä model to obtain the corresponding ion composition and
the measured ACFs are used to complement the model predictions. The
autocorrelation analysis of the time series formed with the measured
densities at all heights also allows the study of the fluctuations in
the ion composition and the estimation of the ionisation lifetime.
Presented in session: 2.02.