Environmental Engineering Reference
In-Depth Information
Figure 6.10 As a result of interaction with
the solar wind, the comet tails consisting of
ions and dust particles are separated from the
comet nucleus, but because of the action of
magnetic forces the binding between the nu-
cleus and tails is conserved in the course of
comet evolution [97].
of this plasma proceed as described above. Correspondingly, the long lifetime of
trapped ions greatly increases the number density of the plasma of a comet tail.
This number density is 10 3
10 4 cm 3
[14, 15] and exceeds that in the solar wind,
10 4 K [15-17] corresponds to that in the solar
wind. One of the reasons for an increase in the plasma density in a dusty plasma
of comet tails is the formation of trapped ions in the field of dust particles with a
relatively long lifetime.
Thus, in contrast to a laboratory dusty plasma, where dust particles do not influ-
ence the plasma parameters outside of the action of the particle field, dust particles
in the solar system change the parameters of a plasma, created by the solar wind.
In addition, interaction of a cosmic dusty plasma with the magnetic field is of im-
portance and determines the spatial structure of this plasma.
but the electron temperature T e
6.2.4
Screening of the Particle Field in a Dense Ionized Gas
In a dense ionized gas where the mean free path electrons and ions
is small com-
pared with the particle radius r 0 , we use the Fuks formulas (6.7) and (6.9) for the
rates of electron and ion attachement to the particle. This gives the following for-
mula for the number density of electrons N e and ions N i near the particle surface.
λ
N 0 exp(
X )
exp(
X 0 )
N 0 1
exp( X
X 0 )
N e ( R )
D
, N i ( R )
D
. (6.50)
1
exp(
X 0 )
1
exp(
X 0 )
Here R is the distance from the particle, N 0 is the number density of electrons and
ions far from the particle, and X
U ( r 0 )/ T ,where U ( R )isthe
potential energy of electrons at a distance R from the particle and the electron and
ion temperatures T are identical. Note that formulas (6.50) follow from the conser-
vation of the rates of intersection of spheres of different radius for electrons and
ions. According to the character of electron and ion attachment, the number densi-
ties of electrons and ions are zero at the particle surface ( X
D
U ( R )/ T , X 0
D
X 0 ) and tend to the
equilibriumnumber density N 0 of electrons and ions far from the charged particle.
D
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