ON ESTIMATING THE AMPLITUDE OF JOVIAN WHISTLERS OBSERVED BY VOYAGER-1AND IMPLICATIONS CONCERNING LIGHTNING

In this paper we extensively reexamine the amplitude of many whistlers detected by the Voyager 1 and try to deduce information about tile ca usative lightning discharges with the use of our ray-tracing computati ons taking into account the amplitude. As a result; we have derived th e frequency spectra and mean radiation power of the causative lightnin g discharges and have also applied statistical method to the analysis. We can summarize our findings in the following. The average power flu x spectral density of the whistlers falls in a range from 10(-12.7)V(2 )m(-2)Hz(-1) to 10(-11.0)V(2)m(-2)Hz(-1). We calculated the total decr ease of the whistler amplitude from the bottom of the ionosphere towar d the spacecraft, as a range from about 30 to 40 dB. One of the strong est estimated lightning events exhibits a frequency dependence compara ble to the terrestrial one; but its peak frequency seems to be similar to the upward current strokes on the Earth. Moreover, the rather smoo th profile obtained implies a small possibility of the presence of str atified layers in the Jovian ionosphere. Other events possibly have fe atures similar to those of the terrestrial return strokes. We calculat ed the mean radiation power per flash of the lightning in the Jovian a tmosphere for a 1-kHz bandwidth over 60 ms, as a range from the order of 10(2) to 10(5) W. The probability distribution of the radiation pow er in Jupiter is found to follow a lognormal distribution, just as in the terrestrial case.