Environmental Engineering Reference
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from the origin to be
H 0 y
y 2 ,
1
1
H x
D
y 2 C
a ) 2
a ) 2
( x
C
( x
C
C
H 0
y 2 ,
x
a
x
C
a
H y
D
y 2 C
( x
a ) 2
C
( x
C
a ) 2
C
where H 0
2 I /( ca ). From this it follows that the energy released from reconnec-
tion of these currents can be estimated to be
D
Z H 2
8
I 2 l
c 2
ε D
d r
.
π
This means that the energy released per unit length of the conductors is constant
near them.
This estimate can be used for understanding the general properties of a turbu-
lent plasma of high conductivity in a magnetic field. The plasma is characterized by
a typical drift velocity v of the electrons, and a typical length
r over which this ve-
locity varies. The energy of this plasma is contained both in the plasma motion and
in its magnetic fields, which are of the order of H
Δ
r ), where N e is the
number density of electrons. As a result of reconnection of magnetic lines of force
and reconnection of currents, transformation of the plasma magnetic energy into
energy of plasma motion takes place, followed by an inverse transformation. In the
end, these forms of energy will be transformed into heat. A typical time for recon-
nection is
eN e v /( c
Δ
. This plasma can be supported by external fields. Figure 4.30
gives an example of reconnection of magnetic lines of force. Released energy is
transferred to a plasma and generates intense plasma flows. This phenomenon is
of importance for the Sun's plasma. The resulting plasma flow inside the Sun cre-
ates a shock wave that is responsible for generation of X-rays. The plasma flows
outside the Sun generate a hot plasma in the Sun's corona.
τ Δ
r /
v
Figure 4.30 Reconnection of magnetic lines of force: (a) before reconnection; (b) after recon-
nection. A dark plasma which produces a pulse as a result of reconnection of magnetic lines of
force moves in two opposite directions perpendicular to these lines.
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