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Mini-magnetospheres and Moon-magnetosphere interactions: Overview Moon-magnetosphere Interactions

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 Added by Joachim Saur
 Publication date 2019
  fields Physics
and research's language is English
 Authors Joachim Saur




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Moon-magnetosphere interaction stands for the interaction of magnetospheric plasma with an orbiting moon. Observations and modeling of moon-magnetosphere interaction is a highly interesting area of space physics because it helps to better understand the basic physics of plasma flows in the universe and it provides geophysical information about the interior of the moons. Moon-magnetosphere interaction is caused by the flow of magnetospheric plasma relative to the orbital motions of the moons. The relative velocity is usually slower than the Alfven velocity of the plasma around the moons. Thus the interaction generally forms Alfven wings instead of bow shocks in front of the moons. The local interaction, i.e., the interaction within several moon radii, is controlled by properties of the atmospheres, ionospheres, surfaces, nearby dust-populations, the interiors of the moons as well as the properties of the magnetospheric plasma around the moons. The far-field interaction, i.e., the interaction further away than a few moon radii, is dominated by the magnetospheric plasma and the fields, but it still carries information about the properties of the moons. In this chapter we review the basic physics of moon-magnetosphere interaction. We also give a short tour through the solar system highlighting the important findings at the major moons.



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In this paper, we study a simple model of an orbiting protoplanet in a central magnetospheric cavity, the entry into such a cavity having been proposed as a mechanism for halting inward orbital migration. We have calculated the gravitational interaction of the protoplanet with the magnetosphere using a local model and determined the rate of evolution of the orbit. The interaction is found to be determined by the outward flux of MHD waves and thus the possibility of the existence of such waves in the cavity is significant. The estimated orbital evolution rates due to gravitational and other interactions with the magnetosphere are unlikely to be significant during protoplanetary disk lifetimes.
The Earth-Moon system is unusual in several respects. The Moon is roughly 1/4 the radius of the Earth - a larger satellite-to-planet size ratio than all known satellites other than Plutos Charon. The Moon has a tiny core, perhaps with only ~1% of its mass, in contrast to Earth whose core contains nearly 30% of its mass. The Earth-Moon system has a high total angular momentum, implying a rapidly spinning Earth when the Moon formed. In addition, the early Moon was hot and at least partially molten with a deep magma ocean. Identification of a model for lunar origin that can satisfactorily explain all of these features has been the focus of decades of research.
We carry out two-dimensional global particle-in-cell simulations of the interaction between the solar wind and a dipole field to study the formation of the bow shock and magnetosphere. A self-reforming bow shock ahead of a dipole field is presented by using relatively high temporal-spatial resolutions. We find that (1) the bow shock and the magnetosphere are formed and reach a quasi-stable state after several ion cyclotron periods, and (2) under the Bz southward solar wind condition the bow shock undergoes a self-reformation for low b{eta}i and high MA. Simultaneously, a magnetic reconnection in the magnetotail is found. For high b{eta}i and low MA, the shock becomes quasi-stationary, and the magnetotail reconnection disappears. In addition, (3) the magnetopause deflects the magnetosheath plasmas. The sheath particles injected at the quasi-perpendicular region of the bow shock can be convected to downstream of an oblique shock region. A fraction of these sheath particles can leak out from the magnetosheath at the wings of the bow shock. Hence, the downstream situation is more complicated than that for a planar shock produced in local simulations.
152 - J. D. Nichols 2012
In this paper we consider the magnetosphere-ionosphere (M-I) coupling at Jupiter-like exoplanets with internal plasma sources such as volcanic moons, and we have determined the best candidates for detection of these radio emissions by estimating the maximum spectral flux density expected from planets orbiting stars within 25 pc using data listed in the NASA/IPAC/NExScI Star and Exoplanet Database (NStED). In total we identify 91 potential targets, of which 40 already host planets and 51 have stellar X-ray luminosity 100 times the solar value. In general, we find that stronger planetary field strength, combined with faster rotation rate, higher stellar XUV luminosity, and lower stellar wind dynamic pressure results in higher radio power. The top two targets for each category are $epsilon$ Eri and HIP 85523, and CPD-28 332 and FF And.
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