A renaissance is being observed currently in investigations of the Moon. The Luna-25 and Luna-27 missions are being prepared in Russia. At the same time, in connection with the future lunar missions, theory investigations of dust and dusty plasmas at the Moon are being carried out by scientists of the Space Research Institute of the Russian Academy of Sciences. Here, the corresponding results are reviewed briefly. We present the main theory results of these investigations concerning the lunar dusty plasmas. We show, in particular, the absence of the dead zone near a lunar latitude of 80 where, as was assumed earlier, dust particles cannot rise over the surface of the Moon. This indicates that there are no significant constraints on the Moon landing sites for future lunar missions that will study dust in the surface layer of the Moon. We demonstrate that the electrostatically ejected dust population can exist in the near-surface layer over the Moon while the dust appearing in the lunar exosphere owing to impacts of meteoroids present everywhere. The calculated values of number densities at high altitudes of the particles formed as a result of the impacts of meteoroids with the lunar surface are in accordance (up to an order of magnitude) with the data obtained by the recent NASA mission LADEE. Finally, we formulate new problems concerning the dusty plasma over the lunar surface.
One of the complicating factors of the future robotic and human lunar landing missions is the influence of the dust. The upper insulating regolith layer is electrically charged by the solar ultraviolet radiation and the flow of solar wind particles. Resulted electric charge and thus surface potential depend on the lunar local time, latitude and the electrical properties of the regolith. Understanding of mechanisms of the dust electric charging, dust levitation and electric charging of a lander on the lunar surface is essential for interpretation of measurements of the instruments of the Luna-Glob lander payload, e.g. the Dust Impact sensor and the Langmuir Probe. One of the tools, which allows simulating the electric charging of the regolith and lander and also the transport and deposition of the dust particles on the lander surface, is the recently developed Spacecraft Plasma Interaction Software toolkit, called the SPIS-DUST. This paper describes the SPIS-DUST numerical simulation of the interaction between the solar wind plasma, ultraviolet radiation, regolith and a lander and presents as result qualitative and quantitative data of charging the surfaces, plasma sheath and its influence on spacecraft sensors, dust dynamics. The model takes into account the geometry of the Luna-Glob lander, the electric properties of materials used on the lander surface, as well as Luna-Glob landing place. Initial conditions are chosen using current theoretical models of formation of dusty plasma exosphere and levitating charged dust particles. Simulation for the three cases (local lunar noon, evening and sunset) showed us the surrounding plasma sheath around the spacecraft which gives a significant potential bias in the spacecraft vicinity. This bias influences on the spacecraft sensors but with SPIS software we can estimate the potential of uninfluenced plasma with the data from the plasma sensors (Langmuir probes). SPIS-DUST modification allows us to get the dust dynamics properties. For our three cases we've obtained the dust densities around the spacecraft and near the surface of the Moon. As another practical result of this work we can count a suggestion of improving of dusty plasma instrument for the next mission: it must be valuable to relocate the plasma sensors to a distant boom at some distance from the spacecraft.
mpact-generated dust clouds were recognized by spacecraft observations around several planetary satellites, including the Moon. Here we propose a method of recovering the initial velocity distribution of ejecta particles on a satellite surface by spacecraft measurements of dust densities at different altitudes. It is shown that this problem can be reduced to the Abelian integral equation. Solution of this equation allows us to restore the ejecta velocity distribution through the use of experimental data.
We investigate the current sheet (CS) of the Venusian magnetotail using the data collected by the Venus Express mission in 2006–2010. We have found that the observed profiles of the main magnetic field component Bx have single-scale or double-scale structures. For single-scale CSs the Bx profile is well approximated by the Harris model, (T0 is the characteristic temporal scale, B0 is the magnetic field at the CS boundary). For double-scale CSs the Bx profile is better described by the double-scale model, with B2>0.3B0 and T2>2T1. The magnetic field component perpendicular to the CS plane and the shear component are on average uniform across CSs and ten times smaller than the amplitude of Bx. The observed Bxprofiles can be described by the quasiadiabatic CS model. According to our interpretation the electric current in single-scale CSs is generally carried by protons on transient orbits. In double-scale CSs the current density is provided by transient protons and oxygen ions. In this case, the inner CS scale is supported by the proton population, while the outer scale is supported by the oxygen population. We suggest that the Venusian CS thickness is likely several ion thermal gyroradii.