ИСТИНА

COSMIC/FORMOSAT-3 RO data on vertical profiles of electron content were used for analysis of the ionospheric dynamics at middle latitudes over Irkutsk region (geo: 53, 103, mag: 42.6, 175.7) during severe magnetic storm on 14-15 December 2006. The storm was accompanied by intense substorm activity and electron precipitation over Irkutsk that resulted in black-outs of ionosonde signals in postmidnight local time sector. Analysis of vertical profiles of electron content permitted to find that the black-out on December 14 was caused by strong ionospheric scintillations. The black-out on December 15 was due to development of a strong layer of ionization in the bottomside ionosphere. These effects demonstrate strong direct impact of the auroral activity on the mid-latitude ionosphere during geomagnetic storms.