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Subauroral polarization streams (SAPS) are narrow channels of strong westward ion flows in both the subauroral ionosphere and the conjugated inner magnetosphere in the nightside during geomagnetic storms and substorms. The SAPS exhibit different types of structures like single-peak, double-peak, multi-peak, and oscillation structures. The SAPS are closely related with ionospheric conductivity and region-2 field-aligned currents. The existence of multiple types of SAPS likely indicates precipitations from different magnetosphere-ionosphere coupling dynamics.

Global observations of electron density profile (EDP)from the COSMIC/FORMOSAT-3 satellites were used to investigate, for the first time, the additional stratification of the F2 layer over the equatorial ionosphere on a global scale, which is called F3 layer. The F3 layer in EDP was recognized through the altitude differential profile featured by two maxima existing from 220 km to the peak height of the electron density. Statistical results show that the highest occurrence of F3 layer appears at dip latitude 7∼8°/−7∼−8° for Northern/Southern Hemisphere and is more pronounced during summer months at 10:00–14:00 LT and 20:00–21:00 LT. The occurrence also has a clear longitude dependence during boreal summer, with relatively higher occurrence at −80∼−100°, −20∼20°, 80∼120° and −160∼−170° longitudes, that is possibly associated with the DE3 tide. Meanwhile, the characteristic of the sunset F3 layer is first detected in the COSMIC EDPs, and compared with the features derived from the GIRO stations at Jicamarca, Sao Luis, Fortaleza, Kwajalein, Sanya and Vanimo at IPS. Evidence shows that the local time distribution of the occurrence of the F3 layer can extend to the postsunset time (1800–2100 local time). The sunset F3 layer has a strong seasonal dependence occurring mainly during the summer time and with a preference at Jicamarca. Unlike the daytime F3 layer, the occurrence of the sunset F3 layer clearly increases with increasing solar activity. These features of the dependence on the season, solar activity, and longitude are clearly related to the geomagnetic control of the evening prereversal enhancement of the equatorial zonal electric field and meridional winds modulated by the geomagnetic configuration.

We report preliminary results of a global 3-D ionospheric electron density reanalysis during 2002-2011 based on multi-source data assimilation. The monthly global ionospheric electron density reanalysis has been done by assimilating the quiet days ionospheric data into a data assimilation model constructed using the International Reference Ionosphere (IRI) 2007 model and a Kalman filter technique. These data include global navigation satellite system (GNSS) observations of ionospheric total electron content (TEC) from ground based stations, ionospheric radio occultations by CHAMP, GRACE, COSMIC, SAC-C, Metop-A, and the TerraSAR-X satellites, and Jason-1 and 2 altimeter TEC measurements. The output of the reanalysis are 3-D gridded ionospheric electron densities with temporal and spatial resolutions of 1 hr in universal time, 5o in latitude, 10o in longitude, and ~ 30 km in altitude. The climatological features of the reanalysis results, such as solar activity dependence, seasonal variations, and the global morphology of the ionosphere, agree well with those in the empirical models and observations. The global electron content (GEC) derived from the international GNSS service (IGS) global ionospheric maps (GIM), the observed electron density profiles from the Poker Flat Incoherent Scatter Radar (PFISR) during 2007-2010, and foF2 observed by the global ionosonde network during 2002-2011 are used to validate the reanalysis method. All comparisons show that the reanalysis have smaller deviations and biases than the IRI-2007 predictions. Especially after April 2006 when the six COSMIC satellites were launched, the reanalysis shows significant improvement over the IRI predictions. The obvious overestimation of the low-latitude ionospheric F-region densities by the IRI model during the 23/24 solar minimum is corrected well by the reanalysis. The potential application and improvements of the reanalysis are also discussed.