Galaxies without dark matter halos?

greywolf42 ) writes:
John Park wrote in message
This seems to require that mu.grad(B) is (a) significantly bigger than
nonmagnetic, dissipative forces and (b) proportional to vxB. (mu is the
magnetic moment of a gas molecule, v the velocity of the molecule and B
the magnetic field; all are vectors.) Neither condition seems
to be self-evidently satisfied.

The theoretical conditions you've listed are not necessary. A magnetic
field accelerates ALL gas in the region.

But why should a mu.grad(B) force have the same direction as a vxB force?

Ionized gas will acclerate (far)
more quickly than neutral gas.

"Far more" sounds right. If the magnetic field gradient is as high as 10
microGauss per kiloparsec, I estimate that, acting on the magnetic moment of a
(neutral) hydrogen atom, over the lifetime of the galaxy, it would produce a
velocity change of the order of 0.1 micrometers per second. This would
correspond to a change in position of the order of 100 light seconds over
the lifetime of the galaxy. Hence my comment about dissipative, nonmagnetic
forces.

--John Park

John Park wrote in message
...
greywolf42 ) writes:
John Park wrote in message
This seems to require that mu.grad(B) is (a) significantly bigger
than
nonmagnetic, dissipative forces and (b) proportional to vxB. (mu is
the
magnetic moment of a gas molecule, v the velocity of the molecule and B
the magnetic field; all are vectors.) Neither condition seems
to be self-evidently satisfied.

The theoretical conditions you've listed are not necessary. A magnetic
field accelerates ALL gas in the region.

But why should a mu.grad(B) force have the same direction as a vxB
force?

Because the magnetic fields themselves are moving through space. Hence, one
gets a 'dragging along' from both B field and grad B field.

Ionized gas will acclerate (far)
more quickly than neutral gas.

"Far more" sounds right. If the magnetic field gradient is as high as 10
microGauss per kiloparsec,

Where did you come up with this number? The magnetic fields certainly don't
have to be uniform over thousands of parsecs. Plasma filaments (from those
ionized gas regions) should have typical widths on the order of AU to
thousands of AU, not kiloparsecs. And with an 'accepted' magnetic field
strength of 5 micro G, this would be tens of thousands to millions of times
higher gradient. Why don't you at least look at the theories that have been
proposed, before you head off with trying to disprove them?

I estimate that, acting on the magnetic moment of a
(neutral) hydrogen atom,

You should have used hydrogen GAS. Which is normally a molecule: H2. And
has a larger moment.

over the lifetime of the galaxy, it would produce a
velocity change of the order of 0.1 micrometers per second. This would
correspond to a change in position of the order of 100 light seconds over
the lifetime of the galaxy. Hence my comment about dissipative,
nonmagnetic forces.

Well, if you assume an arbitrarily close to zero field gradient, apply it to
an atom instead of the molecules found in the real galaxy, you get zero
results.

But, if you don't like the potential for magnetic gradient's there's the
standard interpretation that ionized gas clouds and non-ionized gas clouds
roughly maintain equal pressures between region boundaries. ("Galaxies:
Structure and Evolution", R.J. Tayler) Hence, once you 'drive' the ionized
clouds, you will literally drag the non-ionized clouds around.

greywolf42
ubi dubium ibi libertas

John Park wrote in message
...
greywolf42 ) writes:
John Park wrote in message
This seems to require that mu.grad(B) is (a) significantly bigger
than
nonmagnetic, dissipative forces and (b) proportional to vxB. (mu is
the
magnetic moment of a gas molecule, v the velocity of the molecule and B
the magnetic field; all are vectors.) Neither condition seems
to be self-evidently satisfied.

The theoretical conditions you've listed are not necessary. A magnetic
field accelerates ALL gas in the region.

But why should a mu.grad(B) force have the same direction as a vxB
force?

Because the magnetic fields themselves are moving through space. Hence, one
gets a 'dragging along' from both B field and grad B field.

Ionized gas will acclerate (far)
more quickly than neutral gas.

"Far more" sounds right. If the magnetic field gradient is as high as 10
microGauss per kiloparsec,

Where did you come up with this number? The magnetic fields certainly don't
have to be uniform over thousands of parsecs. Plasma filaments (from those
ionized gas regions) should have typical widths on the order of AU to
thousands of AU, not kiloparsecs. And with an 'accepted' magnetic field
strength of 5 micro G, this would be tens of thousands to millions of times
higher gradient. Why don't you at least look at the theories that have been
proposed, before you head off with trying to disprove them?

I estimate that, acting on the magnetic moment of a
(neutral) hydrogen atom,

You should have used hydrogen GAS. Which is normally a molecule: H2. And
has a larger moment.

over the lifetime of the galaxy, it would produce a
velocity change of the order of 0.1 micrometers per second. This would
correspond to a change in position of the order of 100 light seconds over
the lifetime of the galaxy. Hence my comment about dissipative,
nonmagnetic forces.

Well, if you assume an arbitrarily close to zero field gradient, apply it to
an atom instead of the molecules found in the real galaxy, you get zero
results.

But, if you don't like the potential for magnetic gradient's there's the
standard interpretation that ionized gas clouds and non-ionized gas clouds
roughly maintain equal pressures between region boundaries. ("Galaxies:
Structure and Evolution", R.J. Tayler) Hence, once you 'drive' the ionized
clouds, you will literally drag the non-ionized clouds around.

greywolf42
ubi dubium ibi libertas

greywolf42 ) writes:
John Park wrote in message
...

But why should a mu.grad(B) force have the same direction as a vxB
force?

Because the magnetic fields themselves are moving through space. Hence, one
gets a 'dragging along' from both B field and grad B field.

How do you know they're both "dragging" forces?

Ionized gas will acclerate (far)
more quickly than neutral gas.

"Far more" sounds right. If the magnetic field gradient is as high as 10
microGauss per kiloparsec,

Where did you come up with this number? The magnetic fields certainly don't
have to be uniform over thousands of parsecs. Plasma filaments (from those
ionized gas regions) should have typical widths on the order of AU to
thousands of AU, not kiloparsecs. And with an 'accepted' magnetic field
strength of 5 micro G, this would be tens of thousands to millions of times
higher gradient. Why don't you at least look at the theories that have been
proposed, before you head off with trying to disprove them?

So we have fairly local effects leading to changes of the order of 1 AU
per hundred million years. Still not very impressive.

I estimate that, acting on the magnetic moment of a
(neutral) hydrogen atom,

You should have used hydrogen GAS. Which is normally a molecule: H2. And
has a larger moment.

No, I was being generous: H2 is diamagnetic; H is paramagnetic.

--John Park

greywolf42 ) writes:
John Park wrote in message
...

But why should a mu.grad(B) force have the same direction as a vxB
force?

Because the magnetic fields themselves are moving through space. Hence, one
gets a 'dragging along' from both B field and grad B field.

How do you know they're both "dragging" forces?

Ionized gas will acclerate (far)
more quickly than neutral gas.

"Far more" sounds right. If the magnetic field gradient is as high as 10
microGauss per kiloparsec,

Where did you come up with this number? The magnetic fields certainly don't
have to be uniform over thousands of parsecs. Plasma filaments (from those
ionized gas regions) should have typical widths on the order of AU to
thousands of AU, not kiloparsecs. And with an 'accepted' magnetic field
strength of 5 micro G, this would be tens of thousands to millions of times
higher gradient. Why don't you at least look at the theories that have been
proposed, before you head off with trying to disprove them?

So we have fairly local effects leading to changes of the order of 1 AU
per hundred million years. Still not very impressive.

I estimate that, acting on the magnetic moment of a
(neutral) hydrogen atom,

You should have used hydrogen GAS. Which is normally a molecule: H2. And
has a larger moment.

No, I was being generous: H2 is diamagnetic; H is paramagnetic.

--John Park

John Park wrote in message
...
greywolf42 ) writes:
John Park wrote in message
...

But why should a mu.grad(B) force have the same direction as a vxB
force?

Because the magnetic fields themselves are moving through space. Hence,
one
gets a 'dragging along' from both B field and grad B field.

How do you know they're both "dragging" forces?

Because the plasma filaments are structures that contain roughly cylindrical
fields. As each filament moves by the gas, it will impart a net
acceleration to the gas.

Ionized gas will acclerate (far)
more quickly than neutral gas.

"Far more" sounds right. If the magnetic field gradient is as high as
10
microGauss per kiloparsec,

Where did you come up with this number? The magnetic fields certainly
don't
have to be uniform over thousands of parsecs. Plasma filaments (from
those
ionized gas regions) should have typical widths on the order of AU to
thousands of AU, not kiloparsecs. And with an 'accepted' magnetic field
strength of 5 micro G, this would be tens of thousands to millions of
times
higher gradient. Why don't you at least look at the theories that have
been
proposed, before you head off with trying to disprove them?

So we have fairly local effects leading to changes of the order of 1 AU
per hundred million years. Still not very impressive.

All acceleration is 'local.' The atoms and molecules of gas are 'local.'

I estimate that, acting on the magnetic moment of a
(neutral) hydrogen atom,

You should have used hydrogen GAS. Which is normally a molecule: H2.
And
has a larger moment.

No, I was being generous: H2 is diamagnetic; H is paramagnetic.

Makes no difference.

{AH! The classic 'invisible' snip!}
=========================
over the lifetime of the galaxy, it would produce a
velocity change of the order of 0.1 micrometers per second. This would
correspond to a change in position of the order of 100 light seconds over
the lifetime of the galaxy. Hence my comment about dissipative,
nonmagnetic forces.

Well, if you assume an arbitrarily close to zero field gradient, apply it to
an atom instead of the molecules found in the real galaxy, you get zero
results.

But, if you don't like the potential for magnetic gradient's there's the
standard interpretation that ionized gas clouds and non-ionized gas clouds
roughly maintain equal pressures between region boundaries. ("Galaxies:
Structure and Evolution", R.J. Tayler) Hence, once you 'drive' the ionized
clouds, you will literally drag the non-ionized clouds around.
=========================

Quite simply, John deleted that with which he couldn't argue.

greywolf42
ubi dubium ibi libertas

John Park wrote in message
...
greywolf42 ) writes:
John Park wrote in message
...

But why should a mu.grad(B) force have the same direction as a vxB
force?

Because the magnetic fields themselves are moving through space. Hence,
one
gets a 'dragging along' from both B field and grad B field.

How do you know they're both "dragging" forces?

Because the plasma filaments are structures that contain roughly cylindrical
fields. As each filament moves by the gas, it will impart a net
acceleration to the gas.

Ionized gas will acclerate (far)
more quickly than neutral gas.

"Far more" sounds right. If the magnetic field gradient is as high as
10
microGauss per kiloparsec,

Where did you come up with this number? The magnetic fields certainly
don't
have to be uniform over thousands of parsecs. Plasma filaments (from
those
ionized gas regions) should have typical widths on the order of AU to
thousands of AU, not kiloparsecs. And with an 'accepted' magnetic field
strength of 5 micro G, this would be tens of thousands to millions of
times
higher gradient. Why don't you at least look at the theories that have
been
proposed, before you head off with trying to disprove them?

So we have fairly local effects leading to changes of the order of 1 AU
per hundred million years. Still not very impressive.

All acceleration is 'local.' The atoms and molecules of gas are 'local.'

I estimate that, acting on the magnetic moment of a
(neutral) hydrogen atom,

You should have used hydrogen GAS. Which is normally a molecule: H2.
And
has a larger moment.

No, I was being generous: H2 is diamagnetic; H is paramagnetic.

Makes no difference.

{AH! The classic 'invisible' snip!}
=========================
over the lifetime of the galaxy, it would produce a
velocity change of the order of 0.1 micrometers per second. This would
correspond to a change in position of the order of 100 light seconds over
the lifetime of the galaxy. Hence my comment about dissipative,
nonmagnetic forces.

Well, if you assume an arbitrarily close to zero field gradient, apply it to
an atom instead of the molecules found in the real galaxy, you get zero
results.

But, if you don't like the potential for magnetic gradient's there's the
standard interpretation that ionized gas clouds and non-ionized gas clouds
roughly maintain equal pressures between region boundaries. ("Galaxies:
Structure and Evolution", R.J. Tayler) Hence, once you 'drive' the ionized
clouds, you will literally drag the non-ionized clouds around.
=========================

Quite simply, John deleted that with which he couldn't argue.

greywolf42
ubi dubium ibi libertas

greywolf42 ) writes:
John Park wrote in message
...
greywolf42 ) writes:
John Park wrote in message
...

But why should a mu.grad(B) force have the same direction as a vxB
force?

Because the magnetic fields themselves are moving through space. Hence,
one
gets a 'dragging along' from both B field and grad B field.

How do you know they're both "dragging" forces?

Because the plasma filaments are structures that contain roughly cylindrical
fields. As each filament moves by the gas, it will impart a net
acceleration to the gas.

Acceleration, maybe. Maybe. But why "drag", rather than repulsion, say?
[...]

You should have used hydrogen GAS. Which is normally a molecule: H2.
And
has a larger moment.

No, I was being generous: H2 is diamagnetic; H is paramagnetic.

Makes no difference.

Care to quote the relevant magnetic moments?

{AH! The classic 'invisible' snip!}
=========================

But, if you don't like the potential for magnetic gradient's there's the
standard interpretation that ionized gas clouds and non-ionized gas clouds
roughly maintain equal pressures between region boundaries. ("Galaxies:
Structure and Evolution", R.J. Tayler) Hence, once you 'drive' the ionized
clouds, you will literally drag the non-ionized clouds around.
=========================

Quite simply, John deleted that with which he couldn't argue.

Quite simply, I was addressing the basic physics question of whether a
magnetic field would accelerate neutral and ionised gases in the same way.
How this fits into your other arguments is a separate issue, and one I
have no strong views on, at the moment.

--John Park

greywolf42 ) writes:
John Park wrote in message
...
greywolf42 ) writes:
John Park wrote in message
...

But why should a mu.grad(B) force have the same direction as a vxB
force?

Because the magnetic fields themselves are moving through space. Hence,
one
gets a 'dragging along' from both B field and grad B field.

How do you know they're both "dragging" forces?

Because the plasma filaments are structures that contain roughly cylindrical
fields. As each filament moves by the gas, it will impart a net
acceleration to the gas.

Acceleration, maybe. Maybe. But why "drag", rather than repulsion, say?
[...]

You should have used hydrogen GAS. Which is normally a molecule: H2.
And
has a larger moment.

No, I was being generous: H2 is diamagnetic; H is paramagnetic.

Makes no difference.

Care to quote the relevant magnetic moments?

{AH! The classic 'invisible' snip!}
=========================

But, if you don't like the potential for magnetic gradient's there's the
standard interpretation that ionized gas clouds and non-ionized gas clouds
roughly maintain equal pressures between region boundaries. ("Galaxies:
Structure and Evolution", R.J. Tayler) Hence, once you 'drive' the ionized
clouds, you will literally drag the non-ionized clouds around.
=========================

Quite simply, John deleted that with which he couldn't argue.

Quite simply, I was addressing the basic physics question of whether a
magnetic field would accelerate neutral and ionised gases in the same way.
How this fits into your other arguments is a separate issue, and one I
have no strong views on, at the moment.

--John Park

John Park wrote in message
...
greywolf42 ) writes:
John Park wrote in message
...
greywolf42 ) writes:
John Park wrote in message
...

But why should a mu.grad(B) force have the same direction as a vxB
force?

Because the magnetic fields themselves are moving through space.
Hence,
one
gets a 'dragging along' from both B field and grad B field.

How do you know they're both "dragging" forces?

Because the plasma filaments are structures that contain roughly
cylindrical
fields. As each filament moves by the gas, it will impart a net
acceleration to the gas.

Acceleration, maybe. Maybe. But why "drag", rather than repulsion, say?

'Drag' was more descriptive. Use repulsion if it helps the visualization.
After the flimament has passed, the gases have been accelerated to follow
the filament.

[...]

You should have used hydrogen GAS. Which is normally a molecule:
H2. And has a larger moment.

No, I was being generous: H2 is diamagnetic; H is paramagnetic.

Makes no difference.

Care to quote the relevant magnetic moments?

The net effect of the moving filaments is independent of whether the
atom/molecule is paramagnetic or diamagnetic. What has this to do with your
argument?

{AH! The classic 'invisible' snip!}
=========================

{and the 'invisible' snip within the 'invisible' snip -- which I'll ignore
for now}

But, if you don't like the potential for magnetic gradient's there's the
standard interpretation that ionized gas clouds and non-ionized gas
clouds
roughly maintain equal pressures between region boundaries. ("Galaxies:
Structure and Evolution", R.J. Tayler) Hence, once you 'drive' the
ionized
clouds, you will literally drag the non-ionized clouds around.
=========================

Quite simply, John deleted that with which he couldn't argue.

Quite simply, I was addressing the basic physics question of whether a
magnetic field would accelerate neutral and ionised gases in the same way.
How this fits into your other arguments is a separate issue, and one I
have no strong views on, at the moment.

The basic physics question under discussion is whether neutral gas will be
accelerated in a disk galaxy undergoing electromagnetically-driven rotation
of ionized gas. Since there were repeated objections to magnetic gradients
affecting the magnetic moments of neutral gas, I provided a second physical
force that might be more palatable.

The issue is not about fundamental EM fields -- but how the motions of
intragalactic gas (observed to be decoupled from stellar motions, but
neutral and ionized gas is coupled) can be explained.

greywolf42
ubi dubium ibi libertas