DE-1 AND COSMOS 1809 OBSERVATIONS OF LOWER-HYBRID WAVES EXCITED BY VLF WHISTLER-MODE WAVES

Past work demonstrates that strong lower hybrid (LH) waves can be exci ted by electromagnetic whistler mode waves throughout large regions of the topside ionosphere and magnetosphere. The effects of the excited LH waves upon the suprathermal ion population in the topside ionospher e and magnetosphere depend upon the distribution of LH wave amplitude with wavelength lambda. The present work reports plasma wave data from the DE-I and COSMOS 1809 spacecraft which suggests that the excited L H wave spectrum has components for which lambda less-than-or-equal-to 3.5 m when excitation occurs at a frequency roughly equal to the local lower hybrid resonance frequency. This wavelength limit is a factor o f approximately 3 below that reported in past work and suggests that t he excited LH waves can interact with suprathermal H+ ions with energy less-than-or-equal-to 6 eV. This finding supports recent work concern ing the heating of suprathermal ions above thunderstorm cells.