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, U.K.
2EISCAT Group, Rutherford Appleton Laboratory, Didcot, U.K.
3Geophysical Observatory, FIN-99600 Sodankylä, Finland
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.