Wave Processes in the Dusty Plasma at Phobos and Deimos
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E PLASMA
Wave Processes in the Dusty Plasma at Phobos and Deimos S. I. Kopnina, b, c, T. I. Morozovaa, and S. I. Popela, c, * a
b
Space Research Institute, Russian Academy of Sciences, Moscow, 117997 Russia Moscow Institute of Physics and Technology (State University), Dolgoprudnyi, Moscow oblast, 141700 Russia c Higher School of Economics, National Research University, Moscow, 101000 Russia *e-mail: [email protected] Received February 8, 2019; revised March 15, 2019; accepted March 25, 2019
Abstract—Linear and nonlinear waves in the near-surface plasma at Phobos and Deimos are considered. It is shown that the motion of the solar wind relative to photoelectrons and charged dust grains violates the isotropy of the electron distribution function in the near-surface plasma at the Martian satellites, which leads to the development of instability and excitation of high-frequency waves with frequencies in the range of Langmuir and electromagnetic waves. Moreover, the propagation of dust acoustic waves, which can be excited, e.g., in the terminator regions of the Martian satellites, is possible. Solutions corresponding to the parameters of the plasma–dust systems over the illuminated parts of the Phobos and Deimos surfaces are found in the form of dust acoustic solitons. The ranges of possible Mach numbers and soliton amplitudes are determined. DOI: 10.1134/S1063780X19080063
1. INTRODUCTION At present, special attention in space research is paid to analyzing the properties and manifestations of dusty plasma near the surfaces of the Martian satellites, Phobos and Deimos [1–4]. The MarsExpress, ExoMars Trace Gas Orbiter, Мars Reconnaissance Orbiter, Маrs Odissey, and other spacecraft are successfully functioning on the Martian orbits. In the framework of the prepared Bumerang (Fobos-Grunt-2) mission, it is planned to find dust grains on the Martian orbits and determine the main parameters of dust grains (momentum, mass, velocity, and charge). Interest in studying Martian satellites is caused, in particular, by the fact that they are more accessible for manned flights than Mars itself due to their weak gravitation. The gravitational accelerations on Phobos and Deimos are a factor of ~10 4 lower that on the Earth; hence, the landing of a spacecraft on them resembles docking with another spacecraft than landing on a planet. According to observations of Viking [5, 6] and MarsExpress [1] spacecrafts, the surfaces of Phobos and Deimos are covered with a dust consisting of small regolith grains formed as a result of micrometeoroid bombardment. The weak gravitation enhances the role of dust on Phobos and Deimos, because even a small perturbation can lead to the formation of massive dust clouds over their surfaces. Like the Moon, Phobos and Deimos have no atmosphere. Therefore, the methods by which dusty plasma near the Martian satellites is described [2–4] are similar to those applied for the Moon [7–19]. The Phobos and Deimos surfaces are charged under the
action of solar radiation and solar wind plasma. Interacting with the s
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