Plasma Physics Seminar ( Phys 769)

Dr. Joe Huba, Naval Research Laboratory Three-dimensional equatorial spread F modeling Equatorial spread F (ESF) is a post-sunset phenomenon in which the equatorial F-region ionosphere becomes unstable: large-scale (10's km) electron density `bubbles' can develop and rise to high altitudes (> 1000 km at times). Associated with the large-scale electron density structures are smaller-scale irregularities that generate turbulence down to length scales as small as 10 cm. ESF is an important space weather concern because it scintillates radio signals that can degrade and disrupt communications and navigation systems. The Naval Research Laboratory (NRL) has recently developed a new three-dimensional code to study equatorial spread F (ESF). The code is based on the comprehensive NRL 3D ionosphere model SAMI3 and includes a potential equation to self-consistently solve for the electric field. The model assumes equipotential field lines so a 2D electrodynamic problem is considered. In this study a narrow wedge of the post-sunset ionosphere is simulated. It is found that (1) bubbles can rise to ~1600 km, (2) extremely steep ion density gradients can develop in both longitude and latitude, (3) upward plasma velocities approach 1 km/s, and (4) the growth time of the instability is about 15 min. These results are shown to be consistent with radar and satellite observations. Return to main page