HR: 1340h
AN: SA33A-1139    [Abstracts]
TI: Extraordinarily High Electron Densities Observed in the Crest of the Post-sunset Equatorial Anomaly, Their Persistence with Solar Rotation and the Evidence of an Enhancement of Maximum Pre-reversal ExB Drift Velocity
AU: * Whalen, J A
EM: James.Whalen@Hanscom.AF.Mil
AF: Air Force Research Laboratory, 29 Randolph Road, Hancom AFB, MA 01731-3010 United States
AB: Extremely high F layer electron densities, possibly the highest ever recorded, were observed in the crests of latitudinal profiles of maximum electron density in the post sunset equatorial anomaly. A chain of ionospheric sounders located in western America recorded values of NmF2 of 6.9, 6.5 and $>$6.5 x10$^{6}$ el/cm$^{3}$ on the 3 days, Feb 14, Mar 13 and Apr 11, 1958. These days were 27 and 29 days apart, so were nearly the same day in 3 successive Carrington solar rotations. The levels indicate extremely high levels of maximum pre-reversal ExB drift velocity (ExBmax) as does the fact that equatorial bubbles were observed on 2 of the days and a bubble was likely to have occurred on the third. However, conditions which are associated with high ExBmax, low Kp and high F10.7, were present, but not at levels that were unusual in relation to the other days in the period. Dst and daytime NmE are also ordinary on these days. Each of the 3 days lies in a period of IMF "away" and possibly near a sector boundary as indicated by high latitude magnetograms. Proximity to a boundary is also not unique to these 3 days, but the recurrence with solar rotation suggests that sector structure may play a role. In addition to the remarkable recurrence in solar rotation, the significance of these observations is that they indicate the presence of some not yet understood mechanism that enhances the eastward electric field, hence ExBmax. Its presence at other times could contribute to the largely unexplained variability of ExBmax, of equatorial bubbles and of the resulting scintillation, so that its understanding could lead to much improved forecasts.
DE: 2411 Electric fields (2712)
DE: 2415 Equatorial ionosphere
DE: 2437 Ionospheric dynamics
DE: 2439 Ionospheric irregularities
DE: 2712 Electric fields (2411)
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting