Global characteristics of occurrence of an additional layer in the ionosphere observed by COSMIC/FORMOSAT-3

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.

There were ~9,400 cases of F3 layer selected out of ~448, 000 occultation events at low and equatorial areas during the period of April 2006 - September 2010. 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. 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 wavenumber-3 diurnal tide (DE3).