Plasma boundaries at Mars: a 3-D simulation study

The interaction of the solar wind with the ionosphere of planet Mars is studied using a three-dimensional hybrid model. Mars has only a weak intrinsic magnetic field, and consequently its ionosphere is directly affected by the solar wind. The gyroradii of the solar wind protons are in the range of several hundred kilometers and therefore comparable with the characteristic scales of the interaction region. Different boundaries emerge from the interaction of the solar wind with the continuously produced ionospheric heavy-ion plasma, which could be identified as a bow shock (BS), ion composition boundary (ICB) and magnetic pile up boundary (MPB), where the latter both turn out to coincide. The simulation results regarding the shape and position of these boundaries are in good agreement with the measurements made by Phobos-2 and MGS spacecraft. It is shown that the positions of these boundaries depend essentially on the ionospheric production rate, the solar wind ram pressure, and the often unconsidered electron temperature of the ionospheric heavy ion plasma. Other consequences are rays of planetary plasma in the tail and heavy ion plasma clouds, which are stripped off from the dayside ICB region by some instability.<br><br> <b>Key words.</b> Magnetospheric physics (solar wind interactions with unmagnetized bodies) – Space plasma physics (discontinuities; numerical simulation studies

3D hybrid simulation code using curvilinear coordinates

A new simulation code using the hybrid approximation for modeling extraterrestial plasma processes is described, which can be used in arbitrary three-dimensional, ordered, hexahedral grid. Maxwell's equations are transformed using common tensor analysis and solved by a finite differening scheme. A particle coalescing technique was adopted to account for difference in cell size. The numerical techniques and some results are presented

From a weak to a strong comet - 3D global hybrid simulation studies

Plasma structures resluting from the solar wind interaction with weak comets are discussed. Numerical simulations using a newly developed hybrid code are presented. The simulations are primarily applied to quantitative data for comet Wirtanen, which will be the target of the Rosetta mission. It is expected that Wirtanen is very weak during the first encounter. The main purpose is the discussion of the different features of the plasma environment, such as the structured cycloidal plasma tail and non-linear Mach cones typical for weak comets and their relation to structures like shocklets, bow shock, diamagnetic cavity and the "classical" magnetotail found at stronger comets. Furthermore, the sensitivity of these various features in dependence on the plasma parameters is investigated

Three-dimensional multispecies hybrid simulation of Titan's highly variable plasma environment

International audienceThe interaction between Titan's ionosphere and the Saturnian magnetospheric plasma flow has been studied by means of a three-dimensional (3-D) hybrid simulation code. In the hybrid model, the electrons form a mass-less, charge-neutralizing fluid, whereas a completely kinetic approach is retained to describe ion dynamics. The model includes up to three ionospheric and two magnetospheric ion species. The interaction gives rise to a pronounced magnetic draping pattern and an ionospheric tail that is highly asymmetric with respect to the direction of the convective electric field. Due to the dependence of the ion gyroradii on the ion mass, ions of different masses become spatially dispersed in the tail region. Therefore, Titan's ionospheric tail may be considered a mass-spectrometer, allowing to distinguish between ion species of different masses. The kinetic nature of this effect is emphasized by comparing the simulation with the results obtained from a simple analytical test-particle model of the pick-up process. Besides, the results clearly illustrate the necessity of taking into account the multi-species nature of the magnetospheric plasma flow in the vicinity of Titan. On the one hand, heavy magnetospheric particles, such as atomic Nitrogen or Oxygen, experience only a slight modification of their flow pattern. On the other hand, light ionospheric ions, e.g. atomic Hydrogen, are clearly deflected around the obstacle, yielding a widening of the magnetic draping pattern perpendicular to the flow direction. The simulation results clearly indicate that the nature of this interaction process, especially the formation of sharply pronounced plasma boundaries in the vicinity of Titan, is extremely sensitive to both the temperature of the magnetospheric ions and the orientation of Titan's dayside ionosphere with respect to the corotating magnetospheric plasma flow

3D hybrid simulations of the interaction of the solar wind with a weak comet

The interaction of the solar wind with weak comets, leading to the formation of the cometary magnetosphere with different types of structures in the solar wind and heavy ion plasmas, is simulated using a three-dimensional hybrid code. The simulations were performed for a wide range of gas production rates (6.2×1026mol/sQ1028mol/s) and for an interplanetary magnetic field which is perpendicular to the incoming solar wind. When Q<8.2×1026mol/s the cometary atmosphere forms a strong cycloid-type tail, whereas for Q1027mol/s the cometary atmosphere forms a cone-type tail and structuring of the coma occurs. The results of these simulations may be applied to other weak massloading sources, e.g., dusty plasmas and cometary ion dynamics in the inner coma, AMPTE releases, and nonmagnetic bodies like Phobos, Deimos or even Pluto. Furthermore, the results presented here may be important for studying the dynamics of the ionized environment near the `Solar Probe' spacecraft in the future

Hybrid simulations of stellar wind interaction with close-in extrasolar planets

A hybrid code has been used for three-dimensional simulations of the stellar wind interaction with the ionosphere of an Earth-sized close-in extrasolar planet. The hybrid code treats electrons as a massless, charge-neutralizing, adiabatic fluid while ions are treated as macroparticles. To study the effects of an expanding ionosphere, a consequence of an expanding atmosphere as for e.g. exoplanet HD 209458 b, we have compared the simulation results for an ordinary stationary ionosphere with the results for an expanding ionosphere. In both cases we can identify bow shock, magnetopause and ion-composition boundary. The expanding ionosphere pushes the bow shock and magnetopause upstream and increases the size of the entire interaction region, creating a large wake behind the planet dominated only by the expanding ionosphere

Plasma environment of magnetized asteroids: a 3-D hybrid simulation study

The interaction of a magnetized asteroid with the solar wind is studied by using a three-dimensional hybrid simulation code (fluid electrons, kinetic ions). When the obstacle's intrinsic magnetic moment is sufficiently strong, the interaction region develops signs of magnetospheric structures. On the one hand, an area from which the solar wind is excluded forms downstream of the obstacle. On the other hand, the interaction region is surrounded by a boundary layer which indicates the presence of a bow shock. By analyzing the trajectories of individual ions, it is demonstrated that kinetic effects have global consequences for the structure of the interaction region