Newsgroups: sci.physics.plasma
From: fcrary@benji.Colorado.EDU (Frank Crary)
Organization: University of Colorado, Boulder
Subject: Re: Can Gravity be Induced?

In article <3aajr8$5fa@mojo.eng.umd.edu>,
Stephen Goodfellow <llrowla@cms.cc.wayne.edu> wrote:
>I am acquainted with the theory suggesting that the lack of the solar
>rotation is caused by the solar wind. It was pointed out in one of
>the articles I used as reference that Jupiter's rapid rotation does
>not seem to have suffered from a 'break'effect. To scale, its satellites
>are much larger, its magnetic field bigger than the Sun.
>Any comments?

First of all, Jupiter's satellites are not much larger, even to
scale. The largest moon of Jupiter masses 1.5E23 kg, 0.0001 times
the mass of Jupiter. The Sun's largest satellite, Jupiter,
masses 0.001 as much as the Sun. To scale, the mass of
Jupiter's satellites is an order of magnitude smaller. I
have no idea what this has to do with plasma effects, but...

Second, I don't think it is reasonable to compare the
solar and jovian magnetic fields. Jupiter has a nice,
stable, (roughly) dipole field; the Sun has a very
unstable field with massive contributions from higher
order terms. Since the two are so radically different,
it doesn't make any sense to simply scale one down
and compare them: They are clearly produced by very
different mechanisms.

As far a Jupiter's rapid rotation goes, this isn't a
real problem. If you apply the popular theories of the
solar wind (i.e. the Webber-Davis model) to Jupiter,
you wouldn't expect a "planetary wind" that would
slow down Jupiter's rotation. This model considers
both temperature and gravity. For a high temperature
and low gravity (specifically, thermal velocities
below the gravitational escape velocity), a strong wind
which would slow down the star (or planet) is implied.
For high gravity relative to the temperature, the
wind is restricted and has no significant affect on
rotation. Applying this model to Jupiter would
suggest a trivial wind and no affect on planetary
rotation: Since Jupiter's atmosphere is fairly cold
and its gravity relatively strong, the Webber-Davis
model predicts no significant planetary wind and
no slowing of Jupiter's rotation.

>I am very interested in finding out if the data from solar neutrinos are
>enough, or will be enough in the future, to build an image of their
>origin.

Solar neutrinos aren't really my field, but my understanding
is that, at the moment, this data does not contribute much
to our understanding of the Sun (first because the data is
only available for a small number of years, and second because
observations of low-energy neutrinos are a very recent
development.) But in the long run, I suspect solar neutrinos
observations will be _very_ important: They are a direct
measurement of the fusion occurring deep in the Sun's
core, possibly the only data on this subject we can
obtain.

Frank Crary
CU Boulder