Though we favour the previous model based on the action of
turbulent magnetic diffusion, let us show that there is also a special
kind of dynamo or amplification mechanism that, in contrast
with the standard
,
quickly reaches steady state conditions, and that also produces the
critical profile of the magnetic field strength.
Let us continue considering azimuthal symmetry. In addition to
terms, let us consider
terms, i.e. the effect based on a
mean value of the quantity
<
.
×
>,
non vanishing in turbulence velocity fields, because the Coriolis
force introduces order into the chaotic turbulence. With this
symmetry the induction equation becomes
![]() | (138) |
![]() | (139) |
![]() | (140) |
If, as in the previous Section, we set BR = 0, Bz constant, and assume steady state conditions, this equation system reduces to
![]() | (141) |
![]() | (142) |
![]() | (143) |
The first equation confirms our previous assumption. The third
equation is very illustrative, as, even if = 0, in the absence of
significant turbulent magnetic diffusion, we again obtain the critical
profile
B
= B
*
. As the first
one informs us that
B
/
z, then the second
just tells us that this solution is compatible with either Bz = 0, or no vertical differential rotation
= 0. It is important to note that we have
obtained the critical profile both without
and including
.
In contrast with other dynamos, this mechanism can reach a steady
state.