Environmental Engineering Reference
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Figure 6.8 The number densities of free
(squares) and trapped (circles) ions near a
particle in a rare ionized gas as a function
of the reduced number density of electrons
and ions of a plasma with T e
T i D 400 K. Open symbols correspond to
the case when free ions dominate, and closed
symbols relate to the case when trapped ions
dominate.
D 1eVand
6.2.3
Interaction of Dust Particles with the Solar Wind
In analyzing the equilibrium between a particle and surrounding rare ionized gas
as a result of attachment of electrons and ions to the particle, we find that trapped
ions are of importance for a low number density of plasma electrons and ions.
This occurs in a dusty plasma in the solar system [83-85] that is formed as a result
of interaction of the solar wind with dust in comet tails and the rings of Saturn,
Jupiter, and Uranus. The basis of these dusty plasmas is the solar wind [12, 13, 86],
which is a plasma flux from the solar corona. The solar wind consists mostly of
electrons and protons and is propagated from the Sun in all directions more or
less uniformly. The solar wind accounts for the loss of approximately 2
10 14
timesthemassoftheSunperyear.Thisplasmafluxvariesas1/ R 2 with increasing
distance R from the Sun. On the basis of the average parameters of the solar wind
on the Earth level, we have that the number densities of electrons and protons
are about 7 cm 3 , the electron temperature is 2
10 5 K, the proton temperature is
10 7 cm/s (this velocity corresponds to a proton
kinetic energy of about 1 keV). When the solar wind encounters dust particles, a
specific dusty plasma is formed [4, 83, 84].
As a demonstration of a cosmic dusty plasma, we consider below two examples
of a cosmic plasma containing dust particles. The first example relates to the rings
of Saturn (see Figure 6.9 [87]). In particular, the E and F rings of Saturn contain ice
particles of size ranging from 0.5 to 10
10 4 K, and the flux velocity is 4
5
m [88, 89] and a typical number density
of ice particles is 30 cm 3 [88]. The sources of the ice particles are the neighbor-
ing satellites: Enceladus for the E ring [24, 90], and Prometheus and Pandora for
the F ring [91]. Simultaneous measurements within the framework of the Cassini
μ
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