ИСТИНА

Generation of long-lasting positive storm at low to middle latitudes in the ionosphere remain one of the unresolved problem of the ionosphere-thermosphere system response to the geomagnetic storms. We studied a storm event occurred on 14-15 December 2006 which was characterized by this feature. We have analyzed the dynamics of the positive storm over the Pacific Ocean using a combination of ground-based GPS vertical total electron content (VTEC) and electron density profiles provided by GPS radio occultation from COSMIC satellites. One of the important factors in the analysis of the ionospheric storm dynamics is consistent choose of the quiet time period. Most of days in December 2006 were characterized by weak or modern solar and geomagnetic activity. A day before the storm (13 December) was not an exception, but this day was referred as a “quiet time” in the previous studies. In contrast, we use a period of 2-4 December as most quiet in the sense of solar and geomagnetic activity. This choice allows much more clear representation of the positive ionospheric storms over the Pacific region on the initial, main and recovery phases of the geomagnetic storm. We showed that the observed ionization enhancements might be related to a mechanism of magnetospheric origin.