TRANSMISSION CHARACTERISTICS OF VLF ELF RADIO-WAVES THROUGH THE JOVIAN IONOSPHERE

The propagation characteristics of whistler-mode waves through the pla usible profiles of the Jovian ionosphere have been investigated by mea ns of full-wave numerical computations. There were three different pro files examined in detail: an irregular profile based on Pioneer measur ements, a more-idealized smoother profile, and a smooth profile with a low-altitude ledge. The whistler transmission losses for the Pioneer profiles with several ledges are found to be extremely large in a wide frequency range from 1 to 10 kHz at both day and night, even at a hig h magnetic latitude. The latitudinal dependence of the transmission lo ss for the smooth electron density profiles corresponding approximatel y to the lower edge of the Pioneer profiles, is estimated such that th e loss at magnetic latitude greater than 50-degrees is less than 10 dB at night and day. But the transmission loss exhibits a dramatic incre ase with the decrease in latitude from 30-degrees approximately 40-deg rees, especially at higher frequency and at day. The presence of a pos sible ledge in the bottom ionosphere is found to result in an oscillat ory behaviour of transmission loss due to the development of a standin g wave pattern between relative density maxima. The possible utilizati on of these theoretical characteristics is suggested to study the coup ling of lightning energy to whistlers in the Jovian magnetosphere and also lightning properties from the whistler observations by future dee p spacecrafts.