Plasma Physics Challenge: Confirm New Plasma Wave Mode Predicted by Space Physics R. F. Benson (1), V. A. Osherovich (2), J. Fainberg (1) and B. W. Reinisch (3) 1 - NASA/Goddard Space Flight Center, Greenbelt, Maryland 2 - L3 Comm/Goddard Space Flight Center, Greenbelt, Maryland 3 - University of Massachusetts Lowell, Lowell, Massachusetts A new plasma wave mode has been proposed to explain plasma emissions stimulated by satellite-borne high-power radio-frequency sounders designed to derive remote electron density profiles from electromagnetic-wave echoes. These sounders also generate electrostatic waves that produce coherent echoes (called plasma resonances because of their appearance on the data records) that occur near harmonics of the electron cyclotron frequency fce, the electron plasma frequency fpe, and the upper-hybrid frequency fuh, where fuh2 = fpe2 + fce2. They also stimulate plasma emissions, at frequencies related to these characteristic frequencies, including a sequence observed at frequencies below fpe and between the fce harmonics. They are known as the Dn resonances because of their diffuse appearance on ionospheric topside-sounder records where they were first observed nearly forty years ago. Five mechanisms have been proposed to explain these resonances. One, based on eigenmodes of cylindrical electromagnetic plasma oscillations [1], predicts the observed frequency spacing of the observed Dn sequence and also that these resonances would be expected in any magnetized plasma where fpe and fce are comparable [2]. In agreement with these predictions the Dn resonances have been stimulated in other space plasmas, including the magnetosphere in spite of much different fpe, fce and electron temperature values, the main controlling parameter being the ratio fpe/fce [3]. An empirical fit to ionospheric topside sounder observations [1] yields fD1 = 0.95(fpefce)1/2. The main challenge remaining is to derive this fundamental frequency, i.e., for n = 1 which is most prominently observed when fpe/fce ť 2 - 4, from kinetic theory (analytically or by numerical simulations) and verify using laboratory experiments. [1] Osherovich, V.A., "Physical nature of the diffuse plasma res-onances in the ionosphere," J. Geophys. Res., vol. 92, pp. 316-320, 1987. [2] Osherovich, V.A., "The physical nature of the upper subsidiary diffuse resonances," J. Geophys. Res., vol. 94, pp. 5530-5532, 1989. [3] Benson, R.F., V.A. Osherovich, J. Fainberg, and B.W. Reinisch, "Classification of IMAGE/RPI-stimulated plasma resonances for the accurate determination of magnetospheric electron-density and magnetic field values," J. Geophys. Res., 108(A5), 1207, doi:10.1029/2002JA009589, 2003. _______________ Presentation at 31st IEEE International Conference on Plasma Science