I did not make much progress toward understanding of the interplanetary
magnetic field but I am convinced that Zeilik goofed (Fig 12.9 page 139).
What he calls "magnetic lines of force" are not lines of B. If they were
the Sun would be a magnetic monipole. The spiral lines of Zeilik are, as
shown in other Astronomy textbooks, streams of plasma (solar wind). In
the stellar frame of reference, with respect to which the center of the
rotating Sun is at rest, the ejected solar flares have two components.
One is radial and another is tangential. Due to gravitational attraction
the trajectory of an escaping gas is spiral.
This is clearly explained by James A. Van Alen, the discoverer of famous
plasma belts. He is the author of a chapter "Magnetospheres, Cosmic Rays
and Interpalnetary Medium" in the "New Solar System" book (3 edition, 1990,
edited by Beitty and Chaikin). Van Allen writes:
"Even though the solar corona ejects gas radially outward into
interplanetary space, the continuous stream takes on, by virtue
of the Sun's rotation, the approximate form of an Archemedian
spiral, as first suggested by Chapman".
The magnetic field lines of Van Allen are closed loops going beyond Pluto
and returning to Sun (Figure 4, page 31). I do not understand this figure.
It shows a blue patch labeled "Current sheet". What kind of current is he
referring to? Can solar wind, a macroscopically neutral stream of ionized
gas, be responsible for a magnetic field? The stream is eventually
dispersed; it does not return to Sun. I must be missing something
important.
Ludwik Kowalski