The plasmasphere electron content estimation on the base of radio-measurements

The plasmaspheric electron content (PEC) was estimated by comparison of GPS TEC observations and FORMOSAT-3/COSMIC radio occultation measurements at the extended solar minimum of cycle 23/24. Results of comparative study revealed that for mid-latitudinal points PEC estimates varied weakly with the time of a day and reached the value of several TECU for the condition of solar minimum. Percentage contribution of PEC to GPS TEC indicated the clear dependence from the time with maximal values (more than 50-60%) during night-time and lesser values (25-45%) during day-time. The comparison between GPS TEC and ISR or RO measurements was performed by analysis of the height-temporal distribution for specific point corresponded to the mid-latitudes of Europe. The contribution of PEC to GPS TEC shows variations with maximal values (more than 70%) during night-time and smaller values (30-45%) during day-time for weak disturbance and quite time and rather high values during strong negative storm (up to 90%) with small changes in time. These changes can be explained by the competing effects of electric fields and winds which tend to raise the layer to the region with lower loss rate and movement of ionospheric plasma to protonosphere.