Abstract:

The EISCAT data are used to confirm the important role of precipitation particles in the ionization rate in the auroral region. The height range of the effective ionization is quite different for particles with different energies. On the other hand, an enhancement of magnetospheric convection often results in decreasing of electron density, N, in the F-layer. During January 28~29,1985, the disturbed profiles of N were very typical, in which N_m (E- layer) >> N (F-layer) and N decreased with height above 147 km. This phenomenan is caused by both energetic particles and intensive convection. During the period of February 16~17, 1993, however, the N (F-layer) increased extremely, while N (E-layer) remained low. This is also a typical profile, but is opposite to the former one. In this case,the particles with lower energy (<1 keV) in the magnetosheath enter directly the high latitude ionosphere through the cusp, and can contribute significantly to the F-layer ionization content.

Key words: precipitation particles, magnetospheric convection, cusp, auroral ionosphere