Re: magnetic lines like these ?

[LUDWIK KOWALSKI <KOWALSKIL@alpha.montclair.edu>]

A private message from X (see below) tries to address my conceptual 
difficulties. I agree that Lenz's law plays an important role in
plasma when if flows through a magnetic field. But I am not able to
use it to explain the directions of the field lines associated with
solar wind. The interplanetary magnetic field lines are supposed to be 
directed along the solar wind; they are not perpendicular to it.  At 
least that is how I interpret what I see in textbooks. 

A picture (Zeilik's Figure 13.28, page 295) shows two solar spots of 
opposite polarity, N and S. Magnetic lines outside the photosphere are 
large arks. A neutral stream of plasma (ionized gas) enters the field 
(from the photosphere below) and the horizontal sections of the 
preexisting lines of B (tops of semicircles from N to S), are bent by 
the stream. The lines of B become parallel to the flow of gas. That is 
what I find so difficult to understand. 
                                                       Ludwik Kowalski
P.S. 

Here is what I would expect. Suppose a preexisting magnetic field, B,
pierced by a column of escaping plasma, is horizontal and that plasma 
moves vertically up. In that case, by Lenz's rule, positive and negative 
ions will start orbiting to produce a field equal and opposite to the 
preexisting field. The orbits are perpendicular to B. A column of plasma
becomes a stream of magnetic dipoles (mixed with neutral particles); the
fields of dipoles are perpendicular to the flow of gas. Plasma does become
magnetized, as suggested by X, but not in the direction parallel to the 
flow of solar wind. The phrase "frozen in" simply states that the 
circulating loops are not rapidly destroyed through random collisions.
This is due to very low density, 10 to 100 particles per cm^3.

What experimental evidence do we have about the ORIENTATION of the field
carried by solar wind?

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A message from X.

> When a magnet is instantly placed on a conductive plate, the field 
> remains expelled from the plate by the induced current. Resistance 
> gradually removes energy, the flowing charges slow, and the field 
> "sinks into" the plate in tens of milliseconds. Standard stuff. If the 
> plate was a perfect conductor, it would take infinite time for the 
> current to decay, and the field would never sink in at all. There is 
> repulsion force between plate and magnet which decays as the current 
> decays.
>
> If the magnet has been on the plate long enough that the current has
> decayed and the fields have penetrated, and if the plate is suddenly
> removed, the plate takes the fields along with it.  Or alternately, the
> changing flux induces a current loop which maintains the fields even 
> when the magnet is not there.  If the plate was a perfect conductor, the
> currents would persist forever, and the penetrated flux would forever
> remained trapped in the plate even with no magnet around.  Similar to
> superconductive flux-pinning phenomena. 
>
> Half way between the above two situations we have "field dragging"
> effects. If a copper plate is swept past a bar magnet, the field "sinks 
> into" the plate partially, current loops are induced, and the moving 
> plate can drag/stretch the field lines as it departs.
>
> Now the following I'm not so sure about.  If a bar magnet was in the
> center of some sort of liquid metal fountain, and the metal was expanding
> outwards asymmetrically (perhaps in a disk shape), then I would expect
> that flows of charge would be induced in the metal so that the outward
> moving metal would drag the loops of b-field along with it.  The field
> around the bar magnet would be distorted into a flat disk rather than
> typical dipole, with loops of flux directed outward along one face of the
> disk, diving through the disk at great distance, then returning inwards
> along the other face of the disk.
>
> If the sun essentially spews conductive plasma from it's equator, and if
> the sun's magnetic dipole is through the poles, then I would expect that
> the moving plasma would drag field lines along with it and distort the
> sun's field radially outwards from the equator.  The extended loops of
> b-field might even neck down, pinch off, and fly away from the sun as
> closed loops which penetrate a gob of moving plasma (with loops of
> charge-flow in the plasma of course, like a 1-turn electromagnet.)
> Electrical resistance would eventually slow the charge flow and collapse
> the field loops, but until it did, the fields might form magnetic bottle
> effects, and maintain "clots" of plasma by magnetic pressure.
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