Environmental Engineering Reference
In-Depth Information
the order of 1:
Z
x
ω
u
(
x
ω
)
D
k
ω
dx
k
ω
x
ω
1.
0
This formula describes self-reversal of spectral lines with a dip at the line center
as shown in Figure 3.12 for the case when the plasma temperature drops sharply
near the plasma boundary. Evidently, the condition for a strong minimum of the
radiation flux (3.92) for the spectral line center has the form
k
0
„
T
1
dT
dx
1
(3.93)
where
„
ω
>
T
.
3.3.7
Radiation from the Solar Photosphere
Radiation transfer may be of importance for a plasma or excited gas of large
size [61]. We analyzed above transfer of resonant radiation in the cases of uniform
and strongly nonuniform radiating plasmas. We now consider a plasma with a
slightly varied temperature, being guided by emission of the solar photosphere,
which is created and governed by the processes
H
C„
ω
e
C
H
!
.
(3.94)
Local thermodynamic equilibrium in the solar photosphere is supported by the
processes
H
C
I
H
$
e
C
H
$
2
e
C
e
C
2
e
C
H .
(3.95)
This equilibrium leads to Saha relations between the number densities of the corre-
sponding particles, and for a quasineutral weakly ionized plasma
N
e
D
N
p
N
H
with a small concentration of negative ions (
N
N
e
)wehave
(
N
0
N
H
)
1/2
exp
exp
T
,
N
3/2
H
4
N
1/2
0
J
2
T
ε
0
N
e
D
N
p
D
,
N
D
m
e
T
2
3/2
N
0
D
.
(3.96)
π
„
2
Here
T
is the temperature,
N
H
,
N
e
,
N
p
,and
N
are the number densities of hydro-
gen atoms, electrons, protons, and negative ions, respectively,
J
D
13.605 eV is the
ionization potential of the hydrogen atom, and
ε
D
J
/2
EA
D
6.048 eV, where
0
0.754 eV is the electron affinity of the hydrogen atom. The radiation flux
j
E
ω
EA
D
of the Sun at the position of the Earth is
R
2
r
2
j
E
ω
D
j
ω
,
