The Naval Research Laboratory SAMI3 (Sami3 is Also a Model of the Ionosphere) code is used to model observed plasmasphere dynamics for 1–5 February 2001, a period of quiet time refilling. The SAMI3 model is driven at high latitudes by the magnetospheric potential calculated by the Weimer05 empirical model, using the observed solar wind. At middle‐to‐low latitudes, the self‐consistent dynamo potential is included, driven by specified winds. During this quiet period we find that the shape of the plasmasphere, at any given time, varies significantly with the wind model even as a similar degree of model‐data agreement is recovered for each of the three wind models used. Diurnal oscillations in the model electron density, which are strong when plotted at fixed magnetic local time, are consistent with the degree of variation seen in the measured densities. In all three cases, SAMI3 compares favorably to the electron density measured in situ by the Imager for Magnetopause‐to‐Aurora Global Exploration spacecraft. Results with no winds or with specific wind effects excluded show that wind‐driven E × B drifts shape the plasmasphere, relative to a round plasmasphere with no winds, and reduce the refilling rate, relative to the higher refilling rate found without winds.

The Naval Research Laboratory first‐principles ionosphere model SAMI3 is used to study the ionospheric effects associated with tsunami‐driven gravity waves. Specifically, the Tohoku‐Oki tsunami of 11 March 2011 is modeled. It is shown that gravity wave‐induced variations in the neutral wind lead to plasma velocity variations both perpendicular and parallel to the geomagnetic field. Moreover, the electric field induced by the neutral wind perturbations can map to the conjugate hemisphere. Thus, electron density variations can be generated in both hemispheres which impact the total electron content (TEC) and 6300 Å airglow emission. It is found that the TEC exhibits variations of ≲0.3em0.3em±0.1 total electron content unit (1 TECU = 1016 el m−2) and the 6300 Å airglow emission variation is up to ∼±2.5% relative to the unperturbed background airglow.

Postsunset equatorial plasma bubble merging is examined using the National Research Laboratory code SAMI3/equatorial spread F. It is found that bubbles merge through an “electrostatic reconnection” process. As multiple bubbles develop, the electrostatic potential associated with one bubble can connect with that of a neighboring bubble: this provides a pathway for the low‐density plasma in one bubble to flow into the adjoining bubble and merge with it. Additionally, high‐speed plasma channels (approximately greater than hundreds of meters per second) can develop during the merging process. Optical data is presented of equatorial plasma bubble evolution that suggests bubble merging occurs in the nighttime equatorial ionosphere.

The Naval Research Laboratory (NRL) SAMI3/equatorial spread F (ESF) three‐dimensional ionosphere model is used to study the initiation and development of the large‐scale plasma bubbles in the postsunset equatorial F region by turbulent gravity waves. The gravity wave turbulence is obtained from a three‐dimensional anelastic, finite‐volume model. We show that the phasing of gravity waves at conjugate regions in the ionosphere can enhance (in phase) or reduce (out of phase) the effective seed of the instability. The nonlocalized nature of the effective seed may contribute to the observed day‐to‐day variability of ESF. Additionally, we find that the zonal and vertical wind perturbations associated with the gravity waves are most effective in seeding ESF bubbles; perturbations of the meridional wind are relatively ineffective.

[1] Conjugate heating effects associated with the upcoming Arecibo heater facility are studied using the NRL ionosphere model SAMI2. A density-dependent, localized heating source is included in the electron temperature equation to model ionospheric radiowave heating. Heating effects are examined as a function of the heating timing and the peak density of the unmodified ionosphere (through the F10.7 index). The simulation results suggest that field-aligned duct formation occur during periods of relatively low electron densities (e.g., during the night). The enhancement of the electron temperature and electron density in the conjugate topside ionosphere ($500 km) could reach respective values of $5% and 25%. Heating losses associated with inelastic electron-neutral (N 2 ) collisions primarily inhibit conjugate effects.