The D-region ion composition and electron density response to strong solar proton events (model simulations)

Fluxes of energetic solar protons penetrate deep into the Earth's polar cap middle atmosphere. Interacting with molecules of the air they cause additional dissociation and ionization, and the formed NOx, OHy and ions enter chemical and ion-molecular reactions. Induced changes of the ionospheric D-layer are modeled by a 1D model of lower ionosphere with chemistry, using neutral species concentrations calculated by a 1D photochemical time-dependent model. Changes of the electron and ion densities, and the most important ionospheric parameters are calculated after SPE with the onset on July 14, 2000 and the results are compared with our results obtained previously for the October 19, 1989 SPE. It is shown that not only electron density increases after SPE, but also the amount of clusters. It is found that the magnitude of the ionospheric response depends on season.