Excitation of high frequency, electrostatic waves in the magnetospheres of the outer planets

Summary form only given, as follows. Observations of high-frequency waves onboard Voyager 1 and 2 show that with their approach to Jupiter, Saturn, and Uranus, electrostatic waves are excited within distances of ten planetary radii. Among the most prominent waves are the n+1/2 cyclotron electron Bernstein modes. The most intense waves are excited intermittently at the local upper hybrid frequency. Although the actual values of the plasma and gyrofrequency vary for the three planets, their relative ratios are comparable. A model of two electron populations, including cold thermal and hot electrons with a loss cone, has been studied. It has been shown that crossing of two kinetic eigenmodes can destabilize the system when the density of the hot distribution and its positive gradient in velocity space are sufficiently large. The effect of perturbations on the distribution function extends the unstable spectrum to higher frequencies above the upper hybrid, whereas the waves below the upper hybrid are enhanced by thermal fluctuations. The nonlinear development has been analyzed with the help of particle simulations.<>