Magnetic pole not coincident with rotational axis

Why is the magnetic pole of many heavenly bodies not aligned with the
axis of rotation?

As best as I can tell no one really knows. According to Wikipedia is
is because of "non-dipole moments," and even in the Earth and Sun the
origin of the magnetic field is not understood so it is not surprising
that subtleties cannot be explained.

Frisbieinstein wrote in news:1217652b-df11-4575-
:

Why is the magnetic pole of many heavenly bodies not aligned with the
axis of rotation?

As best as I can tell no one really knows. According to Wikipedia is
is because of "non-dipole moments," and even in the Earth and Sun the
origin of the magnetic field is not understood so it is not surprising
that subtleties cannot be explained.


Because the dynamo that makes the magnetic poles tends to drift a little.

Dear Frisbieinstein:

On Jun 6, 8:03*pm, Frisbieinstein wrote:
Why is the magnetic pole of many heavenly bodies not
aligned with the axis of rotation?

As the Earth's recorded history has shown, it has been, briefly. But
with pole reversals and such, it seems to be more of a "who cares if
it exactly lines up".

As best as I can tell no one really knows.

We don't know for sure how we have a magnetic field in the first
place, All we have are theories. Theories you seem unwilling to dig
in and learn.

*According to Wikipedia is is because of "non-dipole
moments," and even in the Earth and Sun the origin
of the magnetic field ...

So you feel we would not have a magnetic field if the Sun did not?
The Sun has one, and Venus and Mars do not. How do you reconcile
that?
http://www.astronomynotes.com/solarsys/plantblb.htm

... is not understood so it is not surprising
that subtleties cannot be explained.

How comfortable your armchair must be, to never leave it when
quarterbacking.

David A. Smith

On 6/6/2011 11:03 PM, Frisbieinstein wrote:
Why is the magnetic pole of many heavenly bodies not aligned with the
axis of rotation?

As best as I can tell no one really knows. According to Wikipedia is
is because of "non-dipole moments," and even in the Earth and Sun the
origin of the magnetic field is not understood so it is not surprising
that subtleties cannot be explained.

Even though the force has now been officially united and is called the
Electromagnetic force, the magnetic part is a much more difficult force
to analyse, as it acts in a rotational direction, while the electrical
part acts radially. Prior to the 20th century, they were still
considered separate forces, until the connection to electricity was
found out. Various different levels of fluids produce their own magnetic
fields, and they get added to the main planetary magnetic fields and the
result usually comes out weird. For example there are locations over the
oceans where the Earth's magnetic field is almost nil. Uranus has the
weirdest magnetic field in the Solar System. Neutron stars would have
different layers of fluid which would produce similarly weird magnetic
fields on them.

Yousuf Khan

On Jun 7, 9:55*pm, dlzc wrote:
Dear Frisbieinstein:

On J

We don't know for sure how we have a magnetic field in the first
place, *All we have are theories. *Theories you seem unwilling to dig
in and learn.


**** you, asshole.

On Jun 7, 9:55*pm, dlzc wrote:
Dear Frisbieinstein:

On Jun 6, 8:03*pm, Frisbieinstein wrote:

Why is the magnetic pole of many heavenly bodies not
aligned with the axis of rotation?

As the Earth's recorded history has shown, it has been, briefly. *But
with pole reversals and such, it seems to be more of a "who cares if
it exactly lines up".

As best as I can tell no one really knows.

We don't know for sure how we have a magnetic field in the first
place, *All we have are theories. *Theories you seem unwilling to dig
in and learn.

*According to Wikipedia is is because of "non-dipole
moments," and even in the Earth and Sun the origin
of the magnetic field ...

So you feel we would not have a magnetic field if the Sun did not?

Of course not, asshole.

The Sun has one, and Venus and Mars do not. *How do you reconcile
that?

I don't know that much about it. Stop bullying me, asshole.

How comfortable your armchair must be, to never leave it when
quarterbacking.


**** you, asshole.

On Jun 7, 9:55*pm, dlzc wrote:


Do me a big favor. Put me on your do-not-read list, and never reply
to one of my posts again.

I on my part will endeavor to never read one of your insufferably rude
and supercilious posts again.

If your goal is to anger me with your snide insults, you have
succeeded. Enjoy your success.

Frisbieinstein wrote:
Why is the magnetic pole of many heavenly bodies not aligned with the
axis of rotation?

As best as I can tell no one really knows. According to Wikipedia is
is because of "non-dipole moments," and even in the Earth and Sun the
origin of the magnetic field is not understood so it is not surprising
that subtleties cannot be explained.

That's part of the answer--no one really knows. A very good example of
non-alignment is the magnetic fields of the Ap stars. Properties of these
stars include:

unusual abundances of elements such as rare earths, silicon, chromium,
strontium;
very slow rotation;
abundances are in patches on the surface;
usually found to be single stars, very few in binaries;
very strong magnetic fields (in some cases, many kilogauss);
alignment of principal dipole is oblique, around 45 degrees or even closer
to the equatorial plane in many cases, with very few aligned with the
rotation poles;
strong non-dipole components;
centre of dipole is displaced from the centre of the star;
some of the Ap stars pulsate with very short periods (a few mintues).

There are still vigorous arguments over whether these fields are "fossil
remnants" from the stellar collapse during formation, or generated by some
sort of internal dynamo. If the latter, it is strange that the strongest
fields are found in the slowest rotators.

There is a considerable literature on the subject, so you might be able to
follow this up if you have lots of spare time. Start with a search on
wikipedia (magnetic Ap stars) and follow various links, literature
references, etc.

My understanding (as of a few years ago) is that strong magnetic fields in
some white dwarf stars were hypothesized to be remnants of the magnetic
fields of Ap star progenitors.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

On Jun 6, 11:03*pm, Frisbieinstein wrote:
Why is the magnetic pole of many heavenly bodies not aligned with the
axis of rotation?

As best as I can tell no one really knows.
I think this is incorrect.
In neutron stars, the reason is supposed to be that the surface of
the star is a perfect conductor. The neutronium, doped with electrons
and protons, shows no resistance to electricity. Thus, electric
current can circle the neutron star for an indefinitely long time.
During the collapse of the star, the spinning star causes the
electrons to circulate. The axis of the rest of the star shifts in
direction, but the circulating electrons remain in the same direction
when the surface becomes a perfect conductor.
In the case of the sun and earth, the magnetic fields are caused
by an interaction of the spin with the convection currents. So the
direction of the magnetic field is partly in the direction of the
spin, but it has a component determined by the convection currents.
The convection currents are inhomogenous, so the contribution ot the
electric current is random in direction. So there is a certain
component that fluctuates.
Sometimes in the case of both sun and earth, the magnetic dipole
breaks up altogether. The electric current, instead of going all the
way around the sun, starts surrounding little bubbles of material.
is because of "non-dipole moments," and even in the Earth and Sun the
origin of the magnetic field is not understood so it is not surprising
that subtleties cannot be explained.
That is the mathematical description. However, the cause of the
magnetic field has to do with convection currents. It is partially
understood, but the mathematics for modeling it are complex.
Experimental simulations of these systems have been made with
liquid sodium. Although on a different scale, the qualitative
structure of the magnetic field is observed.

On Jun 6, 11:03*pm, Frisbieinstein wrote:
Why is the magnetic pole of many heavenly bodies not aligned with the
axis of rotation?
Because the direction of the magnetic field is determined partly
by the turbulence in an electrically conductive fluid. The turbulence
adds a certain amount of both randomness and chaos into the magnetic
field. Although the spin of the fluid does create a tendency for the
magnetic field to align, the turbulence partly decouples the magnetic
dipole from the spin.
Note that it is the electrical conductivity that is important
here, not the magnetic susceptibility. The fact that the earth's core
is iron has nothing to do with its magnetic field. At the high
temperatures of the earths core, iron is not magnetic. What is
important is that liquid iron conducts electricity.
The turbulence of the liquid iron due to convection currents is
what causes the magnetic field. The spin is a symmetry breaking
mechanism without which the magnetic dipole would be too weak to
measure. However, the turbulence also helps create the magnetic field.
The turbulence helps establish the direction of the field. Since
turbulence is random, the direction of the magnetic field is partly
random.

As best as I can tell no one really knows.
If the mechanism of magnetic field generation were totally
unknown, we would be unable to simulate it in a laboratory.
Experimental analogs of geodynamic, planetary and stellar systems have
been set up on earth. The fluctuations in direction and strength of
these systems have been modeled by theory.
Natural systems have lots of parameters that are hard to measure.
It is difficult to make a quantitative prediction without measurements
of these parameters. Yet, the qualitative features of these magnetic
fields emerge from both calculations and in earth scale experiments.
Here are some interesting links on experiments done with
“turbulent fluids”.
http://georgehaller.com/phystoday.pdf
“Turbulent Liquid-Sodium Flow Induces Magnetic Dipole in Laboratory
Analogue of Geodynam”
http://www-lgit.obs.ujf-grenoble.fr/...05-J-09634.pdf
“The geodynamo team in Grenoble has designed an experiment to study
flows in the
magnetostrophic regime expected for planetary cores. The set-up
consists of a 40cmdiameter
stainless steel sphere filled with 40 liters of liquid sodium, which
can be
rotated around a vertical axis at angular velocities up to 2000rpm. At
the center of
the sphere, a 15cm-diameter inner sphere is made of a permanent magnet
covered
with copper. After magnetization, this inner sphere will provide a
dipolar magnetic
field reaching 0.15T at its poles. The liquid sodium is set into
motion by differential
rotation of the inner sphere, which is entrained at angular velocities
up to 2000rpm
through a magnetic coupler (see Cardin et al, MHD 2002).”
http://www.oca.eu/etc7/EE250/abstracts/BERHANU.pdf
“Contrary to existing laboratory dynamos, the flow is largely
unconstraint the fluid and the electrical current being free to evolve
in the experimental volume.”

Whether you believe me or not, read up on these magnetic
turbulence dynamos. You may find these experiments fascinating.