Morphology and interpretation of magnetospheric plasma waves at conjugate points during December Solstice

The morphological characteristics of magnetospheric plasma waves (period τ ∼ 18 to 150 sec) detected at conjugate points near L = 4 during the winter solstice are studied. No magnetospheric waves that satisfy an imposed strict selection criterion are observed after ∼1700 LT. Approximately half the 94 accepted events are left-hand polarized. No significant change in the polarization characteristics of the waves is observed as a function of local time. Approximately 16% of the events have opposite polarizations in the two hemispheres. The morphological polarization characteristics are discussed in the context of expected body- and surface-wave polarizations. The observed polarizations do not readily support a surface wave arising from the Kelvin-Helmholtz instability on the magnetopause as a source for all the events. All but two of the left-hand and right-hand wave events were symmetrical about the meridian plane, implying a predominant in-phase oscillation of the H component of the wave at each station and an out-of-phase oscillation of the D component.