Powerful Solar Proton Events of January 2005 and their impact on intensity of the stratospheric polar vortex

In January 2005, a series of powerful Solar Proton Events (SPEs) associated with an increase of flare activity on the Sun was observed. Increases of solar proton fluxes with energies 165-500 MeV allowing particles to reach stratospheric altitudes (∼30 km and below) were registered during the events starting on 15, 16 and 17 January. The strongest event, with particle energies exceeding 500 MeV, took place on 20 January and was accompanied by an increase of the neutron monitor counting rate (Ground Level Enhancement). The events under study resulted in a considerable increase of stratospheric ionization. In this work an impact of these events on intensity of the stratospheric polar vortex playing an important part in the mechanism of solar-atmospheric links is studied. A noticeable intensification of the vortex (increase of western wind velocity) was revealed at all the stratospheric levels in the course of the SPE series under study. It was shown that auroral activity (precipitations of auroral electrons generating bremsstrahlung X-rays) is also a possible factor of the vortex intensification. The obtained results provide evidence that ionization changes associated with powerful SPEs and auroral activity may influence the state of the stratospheric polar vortex on the day-to-day time scale. A possible cause of the vortex intensification seems to be temperature variations associated with changes of chemical composition of the polar stratosphere due to ionisation changes.