Linear and nonlinear kinetic Alfvén waves at Venus*

According to the observations, one of the main mechanisms responsible for the ionospheric escape in Venus is the plasma acceleration. Such meWchanism includes several categories as the wave-particle interaction and field-aligned electric fields. Kinetic Alfvén wave (KAW) with its unique quasi-electrostatic nature was reported to be responsible for energizing particles at the terrestrial ionosphere and evacuating the regions they propagate in. Inspired by these observations we propose that KAWs may contribute as an energization mechanism leading to particle loss in Venus as well. To test this hypothesis, we employ the hydrodynamic description of KAWs in the linear and nonlinear regimes in a plasma composed of a mixture of planetary ions and electrons and solar wind plasma found at Venus’ mantle. The plasma parameters used in this study are adopted from the measurements reported by Pioneer Venus Orbiter and Venus Express. The linear analysis shows the existence of wave structures with wavelengths of ∼10-10² km and frequencies up to ∼5 Hz. While the nonlinear analysis predicts the propagation of ultra-low-frequency structures with a maximum amplitude of ∼0.01-0.034 mV/m and a time duration of 20-30 s. The wave electric pulses were Fourier transformed to result in a broadband electromagnetic noise in the frequency range of ∼0.5-2 Hz.