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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 17, issue 6
Ann. Geophys., 17, 782–793, 1999
https://doi.org/10.1007/s00585-999-0782-1
© European Geosciences Union 1999
Ann. Geophys., 17, 782–793, 1999
https://doi.org/10.1007/s00585-999-0782-1
© European Geosciences Union 1999

  30 Jun 1999

30 Jun 1999

Negative ions in the auroral mesosphere during a PCA event around sunset

C. F. del Pozo3,1, E. Turunen2, and T. Ulich2 C. F. del Pozo et al.
  • 1Department of Physics, University of Wales, Aberystwyth SY23 3BZ, UK
  • 2Sodankyäl Geophysical Observatory, FIN-99600, Finland
  • 3Now at Ionosphere and Propagation Group, Engineering Department, Lancaster University, LA1 4YR, UK
  • E-mail: c.del.pozo@lancaster.ac.uk

Abstract. This is a study of the negative ion chemistry in the mesosphere above Tromsø using a number of EISCAT observations of high energy proton precipitation events during the last solar maximum, and in particular around sunset on 23 October, 1989. In these conditions it is possible to look at the relative importance of the various photodetachment and photodissociation processes controlling the concentration of negative ions. The data analysed are from several UHF GEN11 determinations of the ion-plasma ACF together with the pseudo zero-lag estimate of the `raw' electron density, at heights between 55 km and 85 km, at less than 1 km resolution. The power profiles from the UHF are combined with the 55-ion Sodankylä model to obtain consistent estimates of the electron density, the negative ion concentrations, and the average ion mass with height. The neutral concentrations and ion temperature are given by the MSIS90 model. These parameters are then used to compare the calculated widths of the ion-line with the GEN11 determinations. The ion-line spectrum gives information on the effects of negative ions below 70 km where they are dominant; the spectral width is almost a direct measure of the relative abundance of negative ions.

Key words. Ionosphere (auroral ionosphere; ion chemistry and composition; particle precipitation).

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