HR: 1330h
AN: SM42C-0627    [PDF]
TI: The Role of the DNT Resonance in the Classification of Magnetospheric and Ionospheric Resonances
AU: * Osherovich, V A
EM: vladimir@urap.gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Code 690.2, Greenbelt, MD 20771 United States
AU: Fainberg, J
EM: joseph.fainberg@nasa.gov
AF: NASA Goddard Space Flight Center, Code 692, Greenbelt, MD 20771 United States
AU: Benson, R F
EM: u2rfb@lepvax.gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Code 692, Greenbelt, MD 20771 United States
AB: A prominent sounder-stimulated plasma resonance with a frequency between the upper-hybrid frequency $f_{uh}$ ($f_T$ in ionospheric notation) and the electron plasma frequency $f_{pe}$ ( $f_N$ in ionospheric notation) was first identified and designated as the DNT resonance in ionospheric topside sounder ionograms [Benson, Radio Sci., 17, 167, 1982]. The letter D indicates that it has a diffuse appearance on the topside ionograms. Recently this resonance has also been observed to be stimulated in the magnetosphere by the Radio Plasma Imager (RPI) on the IMAGE satellite [Benson et al., JGR, 108(A5),1207, doi:10.1029/2002JA009589, 2003]. No theory has been offered to explain the formation of the DNT resonance. We will present the theoretical foundation for the following formula for the frequency of DNT which is a function of only $f_{pe}$ and the electron gyrofrequency $f_{ce}$: $F_{DNT}=\sqrt {(F_p^2+1+\sqrt{F_p^4+1})/2}$ where $F_{DNT}=f_{DNT}/f_{ce}$ and $F_p=f_{pe}/f_{ce}$. We will show that this formula reproduces the Alouette 2, ISIS-1 and IMAGE/RPI observations. The results indicate that the use of this formula will provide a valuable additional independent confirming element to the spectral identification of sounder-stimulated plasma resonances in certain $F_p$ ranges. This confidence in spectral classification, in turn, leads to confidence in determining the electron density $N_e$ to within a few per cent even in space plasmas with $N_e < 10$ $cm^{-3}$ where determinations to this accuracy are difficult to achieve.
DE: 2471 Plasma waves and instabilities
DE: 2481 Topside ionosphere
DE: 2700 MAGNETOSPHERIC PHYSICS
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting