  The effects of the solar eclipse of March 20, 2015 on different ionospheric
layers were studied, using vertical ionospheric soundings from the ionosondes
of Rome (41.8N, 12.5E), Gibilmanna (37.9N, 14.0E), and San Vito dei Normanni
(40.6N, 18.0E). The responses of the critical frequencies were investigated
during the solar eclipse, and the formulations used for their estimation were
corrected taking into account the decreased solar irradiance. This effect was
modeled as a Solar Obscuration Factor (SOF) and comparisons with experimental
values were performed. A further study on the occurrence of the sporadic E
layer during the eclipse is presented. When ionogram analysis is limited to 3
days before and 3 days after the eclipse, the appearance of the sporadic E
layer seems to be related to the eclipse. However, when a longer range of days
before and after the eclipse event are taken into account this phenomenon does
not appear so clear. The behavior of a regional adaptive and assimilative 3D
ionospheric model was also tested, assimilating plasma frequency profiles
fp(h). Studying the behavior of the model in such unusual conditions enabled
the introduction of corrections to the foE, foF1, and foF2 formulations,
improving the performances of the model itself.
