A new low-latitude ionospheric model has been developed at the Naval Research Laboratory: Sami2 is Another Model of the Ionosphere (SAMI2). SAMI2 treats the dynamic plasma and chemical evolution of seven ion species (H +, He +, N +, O +, N• +, NO +, and O• +) in the altitude range • 100 km to several thousand kilometers. The ion continuity and momentum equations are solved for all seven 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, includes the E x B drift of a flux tube (both in altitude and in longitude), and includes 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. For example, we have found that ion sound waves, which are supported by ion inertia, may be generated in the topside ionosphere (> 1000 kin) at sunrise and sunset [Huba et al., 2000b]. The neutral species are specified using the Mass Spectrometer Incoherent Scatter model (MSIS86) and the Horizontal Wind Model (HWM93). In this paper we describe in detail the SAMI2 model and present representative results from the model. 1. Introduction Over the past two decades a number of computational models of the ionosphere have been developed. An excellent overview of the most widely used models is given in STEP: Handbook of Ionospheric Models [Schunk, 1996] and by Anderson et al. [1998]. In general, ionospheric models treat the global ionosphere in three parts: low latitude, midlatitude, and high latitude. Low-latitude models (e.g., the Phillips Laboratory global theoretical ionosphere model (GTIM) [Anderson, 1971; Anderson et al., 1996], the University of Alabama field line interhemispheric plasma model (FLIP) [Richards and Tort, 1996], and the Sheffield University plasmasphere-ionosphere model (SUPIM) [Bailey and Balan, 1996]) consider the plasma dynamics along an entire field line from hemisphere to hemisphere. Mid-latitude models (e.g., GTIM [Decker et al., 1994] and the Utah State University time-dependent ionosphere model (TDIM) [Schunk, 1988; Schunk and Sojka, 1996]) typically have the upper boundary •< 1000 kin; additional boundary conditions at the upper boundary (e.g., particle flux, heat flux) must be imposed that are generally not consistent with interhemispheric transport. Finally, high-latitude models (e.g., TDIM, GTIM) also have an upper boundary typically set at 1000 km. However, an important aspect of high latitude models is that magnetospheric effects need to be included: for example, the magnetospheric electric field and auroral precipitation effects. A common feature of these models is that they use empirical neutral atmosphere models such as the Mass Spectrometer Incoherent Scatter model (MSIS) [Hedin, 1987] and the Horizontal Wind Model (HWM) [Hedin et al., 1991] or observed data to specify neutral atmosphere densities and winds. There are also two global ionospheric models that sol...

The local dispersion relation for the lower-hybrid-drift isntability is derived in a fully self-consistent manner including the finite-beta effects associated with (a) transverse electromagnetic perturbations (δB≠0), and (b) resonant and nonresonant h/B0 electron orbit modifications. Moreover, the analysis is carried out for arbitrary values of local β=8πn (Te+Ti)/B02, Te/Ti, ω2pe/ω2ce, and VE/vi. (Here, VE is the cross-field E×B velocity, and vi is the ion thermal speed.) For all parameter regimes studied, the net effect of finite plasma beta is to reduce the maximum growth rate γm of the lower-hybrid-drift instability. The details, however, vary, depending on plasma parameters. For example, if Te≪Ti and VE&lt;vi, then the maximum growth rate is reduced by a factor (1+βi/2)−1/2, relative to the value obtained when βi=8πnTi/B20→0. On the other hand, for Te≈Ti, there exists a critical value of plasma beta (βcr) such that the lower-hybrid-drift instability is completely stabilized (γ&lt;0) for β≳βcr.

The Ionospheric Connection Explorer, or ICON, is a new NASA Explorer mission that will explore the boundary between Earth and space to understand the physical connection between our world and our space environment. This connection is made in the ionosphere, which has long been known to exhibit variability associated with the sun and solar wind. However, it has been recognized in the 21st century that equally significant changes in ionospheric conditions are apparently associated with energy and momentum The Ionospheric Connection Explorer (ICON) mission Edited by Doug Rowland and Thomas J. Immel B T.J. Immel

We present quantitative predictions of the impact of the upcoming total solar eclipse on the ionosphere and plasmasphere using the Naval Research Laboratory (NRL) model Sami3 is Also a Model of the Ionosphere (SAMI3). The eclipse will occur over the continental United States on 21 August 2017. Our simulation results indicate that in the vicinity of the eclipse (1) the total electron content (TEC) decreases by up to ∼ 5 TEC units (TECU; 1 TECU = ×1016 m−2) which is a ∼ 35% decrease in TEC, (2) the electron density decreases by a factor of ∼ 50% in the F region, (3) the electron temperature decreases by up to ∼800 K in the plasmasphere, and (4) the O+ velocity changes from ∼40 m s−1 upward to ∼20 m s−1 downward in the F region. Interestingly, the continental size modification of the ionospheric conductance modifies the global electric field, which should lead to measurable changes in the TEC in the southern conjugate hemisphere ( ≲1 TECU).