HR: 0830h
AN: SA21B-0087    [PDF]
TI: Total Electron Content in Nighttime Equatorial Ionosphere: Theoretical Calculations and Comparisons With Data
AU: * Basu, B
EM: Bamandas.Basu@hanscom.af.mil
AF: Air Force Research Laboratory, 29 Randolph Road, Hanscom AFB, MA 01731 United States
AU: Retterer, J
EM: John.Retterer@hanscom.af.mil
AF: Air Force Research Laboratory, 29 Randolph Road, Hanscom AFB, MA 01731 United States
AU: de La Beaujardiere, O
EM: Odile.de La Beaujardiere@hanscom.af.mil
AF: Air Force Research Laboratory, 29 Randolph Road, Hanscom AFB, MA 01731 United States
AU: Valladares, C
EM: cesar.valladares.1@bc.edu
AF: Boston College, 885 Centre Street, Newton, MA 02459 United States
AB: Theoretical calculations of the electron density distribution in the nighttime equatorial ionosphere are presented. Particular attention is given to the total electron content (TEC) in the Appleton anomaly region and its dependence on the vertical plasma drift velocity, which is enhanced after sunset. The calculations are done by assimilating plasma drift velocity measured by Jicamarca incoherent scatter radar into the low-latitude ambient plasma density model, which has been developed at the Air Force Research Laboratory (AFRL) in support of the C/NOFS mission. Specifically, drift velocity data for fourteen days in 2002 covering a wide range of values for the maximum value of the post-sunset drift velocity are used in the calculations. The latitudinal profiles of the calculated TEC are compared with those obtained from GPS and TOPEX measurements, and are found to be in reasonably good agreement. Relationships between the maximum value of the post-sunset plasma drift velocity and the various parameters that characterize the nighttime anomaly are also examined. It is found that definite linear relationships with statistically significant correlation coefficients exist between the maximum value of the post-sunset drift velocity and the peak-to-valley ratio of anomaly TEC. The significance of this finding lies in the fact that the maximum value of the post-sunset vertical drift velocity is an important, perhaps the most important, plasma parameter for determining both the intensity and the latitudinal distribution of equatorial scintillation. When this plasma parameter is not available from any direct measurement, the linear relationships may be used to estimate it from the peak-to-valley ratio of anomaly TEC, which, in turn, can be derived from the ultraviolet (UV) imagery data of the anomaly region acquired by GUVI on TIMED and hopefully by SSUSI on DMSP and by similar sensor on NPOESS. The theoretically derived linear relationships are compared with similar relationships suggested by the TEC data obtained from GPS measurements.
DE: 2415 Equatorial ionosphere
DE: 2437 Ionospheric dynamics
DE: 2447 Modeling and forecasting
SC: SPA - Aeronomy [SA]
MN: 2003 Fall Meeting