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Mars lacks an intrinsic magnetic field, allowing the solar wind and its embedded interplanetary magnetic field to directly interact with the planet’s dayside ionosphere. During this interaction, energy and momentum from the solar wind are transferred to ions escaping from the ionosphere. This transfer is governed by the structure of the electric field and current systems induced by the solar wind interaction. In a previous study, we mapped the spatial distribution of the energy transfer rate – i.e. the power exerted by the electric field to accelerate planetary ions – using amitis, a high-performance GPU-based hybrid plasma model. In the present study, we further decompose the contributions of different electric field components in Mars’ induced magnetosphere: the motional, Hall, and ambipolar terms, under typical solar wind and ionospheric conditions. Our results show that the motional electric field dominates the energy transfer process across most of the interaction region via mass loading. In particular, the direct energy transfer between the solar wind and planetary ions via the motional electric field is a fundamental characteristic of the Martian induced magnetosphere. The Hall term becomes significant at the base of planetary ion plumes, where magnetic field lines are highly bent and ion densities are elevated. We also find that the motional term contributes more to the energization of planetary ion species with a higher m/q ratio compared to the Hall term. The ambipolar term is generally weak, but it can transport newborn ions to higher altitudes, where they become subject to other electric field components. We illustrate the contributions of each electric field term by tracing their associated power along the trajectories of test particles.

We apply a recently proposed method to estimate heavy ion (O(Formula presented) ) escape from Venus, combining in situ spacecraft observations from Venus Express (VEX) with a hybrid plasma model that treats ions as particles and electrons as a fluid. Using this approach, we examine how various upstream solar conditions – including extreme ultraviolet (EUV) radiation, solar wind dynamic pressure, and the strength and cone angle of the interplanetary magnetic field (IMF) – influence heavy ion loss. Our results show that the heavy ion escape rate exhibits no clear dependence on EUV radiation, possibly due to transport-limited processes. Under low EUV conditions, the escape rate increases with solar wind dynamic pressure, whereas no consistent trend is observed under high EUV. The escape rate decreases with increasing IMF strength and is highest when the solar wind flow is aligned with the IMF (i.e. small cone angle), and lowest when the flow and field are perpendicular. In general, some of these findings agree with what has previously been found for Mars, but Venus appears to be less sensitive to solar variability than Mars.

When the cone angle of the interplanetary magnetic field (IMF) becomes small, induced magnetospheres of unmagnetized planets degenerate. Using hybrid simulations, we study ionospheric ion escape in a 4° cone angle case and compare it with the nominal 55° cone angle (Parker spiral) case. The total escape rate is 1.7×1⁢025 s−1, nearly an order of magnitude higher than the nominal rate of 2.2×1⁢024 s−1. The escape probability is four times higher. The unique feature of the degenerate induced magnetosphere is the upstream escape driven by the ambipolar electric field, contributing 42% to the total escape, a channel absent in the nominal case. Additionally, 52% of escape occurs through a cross-flow plume, formed by the drift of ionospheric ions in the weak convective field and IMF. This channel is dominant, exhibiting an intensity seven times greater than that of the plume driven by the convective electric field in the nominal case.

We refine a recently presented method to estimate ion escape from non-magnetized planets and apply it to Mars. The method combines in-situ observations and a hybrid plasma model (ions as particles, electrons as a fluid). We use measurements from the Mars Atmosphere and Volatile Evolution (MAVEN) mission and Mars Express (MEX) for one orbit on 2015-03-01. Observed upstream solar wind conditions are used as input to the model. We then vary the total ionospheric ion upflux until the solution fits the observed bow shock location. This solution is a self-consistent approximation of the global Mars-solar wind interaction at this moment, for the given upstream conditions. We can then study global properties, such as the heavy ion escape rate. Here we investigate the effects on escape estimates of assumed ionospheric ion composition, solar wind alpha particle concentration and temperature, solar wind velocity aberration, and solar wind electron temperature. We also study the amount of escape in the ion plume and in the tail of the planet. Here we find that estimates of total heavy ion escape are not very sensitive to the composition of the heavy ions, or the amount and temperature of the solar wind alpha particles. We also find that velocity aberration has a minor influence on escape, but that it is sensitive to the solar wind electron temperature. The plume escape is found to contribute 29 % of the total heavy ion escape, in agreement with observations. Heavier ions have a larger fraction of escape in the plume compared to the tail. We also find that the escape estimates scales inversely with the square root of the atomic mass of the escaping ion specie.

We apply a recently proposed method to estimate heavy ion escape from Mars. The method combines in situ observations with a hybrid plasma model, which treats ions as particles and electrons as a fluid. With this method, we investigate how solar upstream conditions, including solar extreme ultraviolet (EUV) radiation, solar wind dynamic pressure, and interplanetary magnetic field (IMF) strength and cone angle, affect the heavy ion loss. The results indicate that the heavy ion escape rate is greater in high EUV conditions. The escape rate increases with increasing solar wind dynamic pressure, and decreases as the IMF strength increases. The ion escape rate is highest when the solar wind is parallel to the IMF and lowest when they are perpendicular. The plume escape rate decreases when the solar wind convective electric field increases.