SAMI2: A New Low-Latitude Ionosphere Model

Joseph D. Huba
Naval Research Laboratory, Washington, DC

A new low-latitude ionospheric model has been developed at the Naval Research Laboratory: SAMI2 (Sami2 is Another Model of the Ionosphere). SAMI2 treats the dynamic plasma and chemical evolution of seven ion species (H+, He+, N+, O+, N2+, NO+, and O2+) in the altitude range 90 km to several thousand km. The ion continuity and momentum equations are solved for all 7 species; the temperature equation is solved for H+, He+, O+, and the electrons. SAMI2 models the plasma along the earth's dipole field from hemisphere to hemisphere. It includes the E x B drift of a flux tube (both in altitude and in longitude) and ion inertia in the ion momentum equation for motion along the dipole field line. The final point is relevant for plasma dynamics at very high altitudes where ion inertia can be important. The neutral species are specified using the empirical models MSIS86 and HWM93. In this talk we describe SAMI2 in detail and present representative results from the model. We also present two new results discovered with SAMI2: (1) the possibile formation of an electron hole (depletion) in the topside equatorial ionosphere and (2) the possible generation of ion sound waves in the topside low latitude ionosphere at sunrise and sunset. This latter result is obtained because ion inertia is included in SAMI2.