Effect of the size of macroparticles on their electrostatic interaction in a plasma |
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Authors: | A V Filippov |
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Institution: | (1) Berkeley, CA, USA; |
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Abstract: | The electrostatic interaction of two spherical macroparticles in a plasma has been considered. Primary attention has been
focused on investigating the electrostatic interaction at short distances where polarization effects of the surface charge
of finite-size macroparticles begin to play a dominant role. The first part of this study is devoted to the interaction of
a point charge with a charged conducting sphere in an equilibrium plasma. It has been shown that the presence of a plasma
in the system leads to a decrease in the potential barrier when two like-charged macroparticles approach each other and that
this decrease proves to be the most significant in the case where the macroparticle radius is comparable to the Debye screening
length. The second part of this study is concerned with the interaction of two conducting spheres in the bispherical system
of the coordinates under the assumption that the charges of the conducting spheres are constant and under the assumption that
the surface potentials of the spheres are constant. The latter case is closer to the physics of electrostatic interaction
of two macroparticles in a plasma medium where the electrostatic potential of their surface is determined by the floating
potential of the plasma. It has been demonstrated that the interaction potentials in these two cases are substantially different
from each other and that, at constant macroparticle charges, the energy of the electrostatic field is an interaction potential,
but, in the case of macroparticles with constant surface potentials, which are independent of the interparticle distance,
the energy of the electrostatic field is not an interaction potential. In the latter case, account must be taken of the work
done by external sources on the macroparticle potentials to maintain them constant. The form of the interaction potential
has been established in this case from the analysis of the interaction force in terms of the Maxwell tension tensor. In the
third part of this study, the interaction of two macroparticles has been considered in the spherical system of coordinates
and analytical expressions for the interaction potentials have been derived for both the case of constant macroparticle charges
and the case of constant surface potentials of the macroparticles. |
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