Can wave-particle interaction be important for ion heating and escape at Venus?

Venus' relatively small induced magnetosphere enables the solar wind to interact directly with the upper atmosphere (Stenberg Wieser et al., 2015), and one could guess that this would yield a larger escape rate compared to a magnetized planet. However, the escape rates reported from Earth are somewhat larger than from Venus. Singly charged oxygen dominates the ion mass outflow from Earth and the average escape rate is estimated to be a few times 10²⁵ s^-1 (André, 2015, and references therein). A strong intrinsic magnetic field creates a huge magnetosphere, which prevents direct solar wind access to the atmosphere, but the big structure instead provides a larger interaction cross section to transfer solar wind energy and momentum into the magnetosphere (e.g., Gunell et al., 2018). This can lead to a larger ion energization and atmospheric escape.

In the absence of a direct interaction between the ionosphere and the solar wind, wave-particle interaction has been identified as a major ion energization process at Earth. Several wave modes at different frequencies are able to heat ions. (André & Yau, 1997). A common type of ion heating is associated with low-frequency broadband electric wavefields (André et al., 1998). The spectral density of such broadband waves does not exhibit a peak at a certain frequency but the wave power available at the ion gyrofrequency may nevertheless efficiently energize the ions (Chang et al., 1986). At Earth this heating mechanism is definitely effective and important (André et al., 1998).

We investigate if ions originating from the Venusian ionosphere can be energized by electric wave power in a similar way as is observed at Earth.

References

André, M. (2015). Previously hidden low-energy ions: a better map of near-earth space and the terrestrial mass balance. Physica Scripta, 90 (12), 128005.

André, M., Norqvist, P., Andersson, L., Eliasson, L., Eriksson, A. I., Blomberg, L. Waldemark, J. (1998). Ion energization mechanisms at 1700 km in the auroral region. Journal of Geophysical Research: Space Physics, 103 (A3), 4199-4222.

André, M., & Yau, A. (1997). Theories and observations of ion energization and outflow in the high latitude magnetosphere. Space Science Reviews, 80 (1), 27-48.

Chang, T., Crew, G. B., Hershkowitz, N., Jasperse, J. R., Retterer, J. M., & Winningham, J. D. (1986). Transverse acceleration of oxygen ions by electromagnetic ion cyclotron resonance with broad band left-hand polarized waves. Geophysical Research Letters, 13 (7), 636-639

Gunell, H., Maggiolo, R., Nilsson, H., Stenberg Wieser, G., Slapak, R., Lindkvist, J., De Keyser, J. (2018). Why an intrinsic magnetic field does not protect a planet against atmospheric escape. A&A, 614.

Stenberg Wieser, G., Ashfaque, M., Nilsson, H., Futaana, Y., Barabash, S., Diéval, C., Zhang, T. L. (2015). Proton and alpha particle precipitation onto the upper atmosphere of venus. Planetary and Space Science, 113-114 , 369-377.