TENTATIVE CONCLUSIONS (ABOUT MAGNETIZED SOLAR WIND)
I know my conclusions below are terribly pretentious. Solar magnetism
was studied by astronomers for many decades. I am not an astronomer,
I am a teacher who just started to learn astronomy from a textbook
written for non-science majors. These tentative conclusions are being
posted because I want to be criticized, and to learn from criticism.
1) A phrase "magnetic field carried by solar wind" makes sense to me
now. It means that plasma ejected from the photosphere passes
through solar magnetic field and become magnetized. The escaping
"wind" contains organized (preferentially oriented) current loops.
2) Magnetization of plasma can be explained via the Lenz's rule.
Positive and negative ions start orbiting to produce a field whose
lines are opposed to the direction of solar field B. Ion loops
travel long distances; they advance in such a way that the orbital
angular momenta are initially perpendicular to speeds. It is like
carrying a magnet from a place where it was manufactured to another
location. Orbits tend to preserve orientations with respect to the
frame of reference of "fixed stars". But sooner or later they are
randomized through collisions or reoriented by the encountered
planetary and galactic fields. They are like sharp blades cutting
into the open space.
For example, if the preexisting solar magnetic field lines are
horizontal, and the plasma velocity is vertical, then ions orbit
along vertical circles whose axes are horizontal. In a uniform field
of B=1000 Gs protons entering with v=1000 km/s will follow the orbits
whose radii are 0.1 meter (or 10 m when B=10 Gs). Due to the mass
differences the orbits of electrons must be correspondingly smaller.
3) If the conclusion 2 is valid then one may NOT say that magnetic field
lines are directed along the paths of solar wind. Solar wind particles
travel over very long distances, up to 100 AU, but the magnetic field
measured at such distances is totally detached from the Sun. Real
solar field loops (detectable with our instruments) are likely to be
confined to a sphere whose radius is not much larger than two coronal
diameters, or so.
4) Magnetized jets of plasma travel along spiral lines because they are
ejected from a rotating sphere. Most jets originate near the solar
equator. They intercept the orbit of Earth at an angle of 45 degrees.
Spiraling does not affect circles along which ions are orbiting in
solar wind streams. The term "frozen in", often used in connection
with the magnetic field of the solar wind, refers to "constant
orientations" of orbiting ions. Such ions have a tendency to
"remember" orientations of solar B which forced them to rotate.
5) Figure 12.19 of Zeilik (on page 258, 8th edition, 1997, "Astronomy,
the Evolving Universe") must be relabeled. The spiraling lines are
streams of solar winds. They are NOT "magnetic lines of force". If
they were then the Sun would be a magnetic monopole. The same applies
to Zeilik's Figure 13.14 on page 287. The term "interplanetary
magnetic field", for the outgoing spiral lines of that figure is
misleading.
I suspect that we have a semantic ambiguity here. A picture nearly
identical to those shown by Zeilik can be found in an advanced
textbook ("Introduction to Space Science by R. C. Haymes, 1971,
page 284). But here the caption refers to the "spiral structure of
the interplanetary magnetic field" rather than to "magnetic field
lines" as in Zeilik. Something was probably lost in the process of
"explaining" a difficult subject to non-specialists. We all goof
once in a while.
6) Figure 4 of Van Allen (page 31 in "The New Solar System" edited by
Beatty and Chaikin, 3rd edition, 1995) is also not consistent with
my mental picture. Magnetic line, stretched beyond Pluto, are now
CLOSED loops. At least the "solar monopole" nonsense is avoided.
But the figure refers to an unexplained current. What is this
current flowing through the loops? I suspect that ... Well, why
should I speculate about what a Nobel laureate had in mind when
the figure was drawn? What experimental evidence do we have that
closed magnetic field loops, emerging from Sun and stretched up
to 100 AU, are real? Was the spectral line splitting method ever
used to identify derections of B lines?
7) Figure 13.28 of Zeilik (on page 295) may also reinforce the idea
that magnetic field lines above corona are parallel to streamlines
of the outflowing plasma. I think that the magnetic field lines of
plasma are perpendicular to streamlines, not parallel. The best way
to falsify the above reasoning would be to determine the direction
of the plasma's field, experimentally. What evidence do we have
about what really happens to ions in the escaping solar wind?
Once again, let me say that the purpose of this posting is to promote
criticism. I would not be surprised to find that I am again missing
something important. I want to know where I am wrong. Zeilik's book
(8th edition now) is as popular in "conceptual astronomy" courses as
Hewitt's book is in "conceptual physics". It is very unlikely that a
significant misconception would not be noticed by so many teachers who
use the text. Zeilik is an expert on solar magnetic activities; he has
A.B. in Physics from Princeton and M.A. plus PH.D in Astronomy from
Harvard. But what do I have to lose in claiming that he goofed?
Please let me know what you think, especially those who teach
astronomy, either in public or in private. I will not be hurt by
criticism. Were you also confused by wrong terminology?