[meteorite-list] other data (Tracy's questions)

From: mexicodoug <mexicodoug_at_meteoritecentral.com>
Date: Tue, 4 Dec 2007 13:28:58 -0600
Message-ID: <007801c836ab$ebf37e50$4001a8c0_at_MICASA>

Tracy wrote:

"Thought experiment... Jupiter is known to have some heavy magnetic fields,
as well as intense radiation. Would an iron asteroid spending several
thousand years or so whipping through Jupiter's magnetic field develop a
notable magnetism of its own? "

Hi Tracy, Listees[3rd posting attempt in 2-1/2 hours :-(]

Probably not magnetized, Great thought either way - and considering even
stony asteroids containing metal flecking are also included. The magnetic
field of Jupiter at it's strongest points near the surface is like being a
centimeter away from a kitchen magnet (~8 Gauss at one centimeter distance,
even thought the magnet manufacturer says it is 3000 Gauss, and at the
surface it is 200 Gauss). Ever notice how a rare earth magnet is nearly
useless just two or three centimeters away - same story even though it is
rated for 15,000 Gauss!

Following Pete's line of thinking, to become magnetized, being in a
not-to-excessive magnetic field isn't enough, the material (iron asteroid in
this case) would have to have a net orientation with respect to the magnetic
flux for the effect to be cumulative. Like the repeated "stroking" he
mentions against a magnet in a lab - in the same direction. There is
nothing magic about the touching of the object to the magnet while
"stroking", just that if it touches, you have the most powerful and parallel
oriented part of the field (radius closer to zero, assuming the magnetic
field drops off with distance from its center: this effect you can see with
the drop off mentioned with the kitchen magnet).

In the case of Jupiter, you obviously wouldn't be touching Jupiter's metal
core (of hydrogen metal), so that would be in the lab like passing
("stroking") the iron to be magnetized without touching. It works fine,
just takes longer and doesn't provide the exposure to the maximum flux
available (thus, decreases the strength of the resulting induced permanent
magnetism).

Some questions to ask:

a) How strong is Jupiter's magnetic field? (maximum already answered,
Jupiter's magnetic field at any asteroid-whipping distance weaker than
Earth's field at Earth's surface.)

b)And how does it decrease with distance from Jupiter (the size of the
field)?

c)Could something pass through Jupiter's magnetic field repeatedly without
being part of the Jovian System (i.e., without orbiting Jupiter)?

d)Under what circumstances could the passes through Jupiter's magnetic field
be cumulative and not randomly counterproductive?

e)What is the field strength in the Tail of Jupiter's magnetic field for
some hapless asteroid caught in plane and between the two giants?

f)Does Jupiter's magnetic field stay stationary at any points (like on Earth
and Mars, a net moment can be recorded at particular points on the
surface.)?

g)If caught in a Kirkwood gap, could an asteroid get close enough making
enough passes, to be magnetized and instead of being captured, be
slingshotted Sunwards?

h) How close would a piece of iron need to pass to Jupiter to get magnetized
enough above the noise ratio enough to be observed qualitatively?

Complicated questions - the observation I have:

If Jupiter's toroidal magnetic field has a 10 million kilometer diameter, at
the edge of the torus, the escape velocity will be about 7.07 km/s, locked
around Jupiter. Earth's escape velocity is 11.19 km/s. Or looked at
another way, to escape from this weak edge of this 10 million km Jupiter
field torus, an object is midway (rms) between Mars and Earth escape
velocity from escaping the rocky planets' ground level. Beyond the edge,
there is not much a net field. Maybe an object orbiting relatively along
Jupiter's field flux line vectors would be magnetized effectively, if such
an orbit were possible (if it were polar, would it need to do a flip each
time it passed one of Jupiter's magnetic poles, haven't though about that.)

So all things considered, along with the fact that Mars has an atmosphere,
maybe the odds of escaping Jupiters magnetic field (while in orbit) are
about as likely as meteoroids from Mars, and this is the edge of the field
where it is weakest. Not saying impossible! Saturn has it's own
asteroid/meteoroid belt - the "rings", so things do collide and something
might escape if it happened just right ... Incidentally - the same would be
true for a fragment from Saturn's rings in your thought question. But the
only authentic Saturn brought to the list's attention so far was the one in
Anne Black's driveway, which hopefully never suffered such a collision :-)

One other observation, is that roughly in the plane of the solar system, the
Sun lifts and pushes back down again her ballerina skirt enough (though at a
factor perhaps only 1/1000 of what Jupiter could do under optimal conditions
closer in to the giant planet) to scramble magnetic moments, and to make
things even more interesting, flips direction every 11 years. I am thinking
about this like a rare meteoroid escaping Jupiter being a videotape that the
Sun incessantly plays, rewinds and fast forwards for millions of years until
the day we get a piece of Jupiter in our driveway (or in my case, just the
sidewalk right of way...), and pop it in the VCR and hope for "contact"...

Hope I've not gotten on too shaky ground with your question, but now it is
time to ask if there is a doctor in the house who can answer it for real?

Best wishes and great health,
Doug

PS, the question on heating from the magnetic field of Jupiter via induced
electrical current, I think you would need to be way too close to have any
hope of observing this. Europa is thought to have a metal core, but it is
shielded by some sort of a conductive ocean. So the satellite moon has its
own independent magnetic field. If we take the case of Jupiter's closest big
satellite, Io, we note it is heated and has volcanos, and is believed to
have a Ni-Iron core. But Io's heat was seen to be generated by Jupiter's
gravitational interaction (frictional compression), and not to have any
magnetic field of its own - basically being a magnetic slave to Jupiter.
Still, it is an interesting case, because the volcanos spew ions that
connect it to Jupiters in an electric circuit in the vast Jovian magnetic
field, and nearly a million amps are generated! The other two big moons of
Jupiter are thought to have basically non metallic cores, so my take-way is
that any power dissapated from such hypothesized eddy currents is minor
compared to other interactions with Jupiter. This is a PS because it is
based on volcanically shaky ground, but I thought you might appreciate that,
living life in that neighborhood of Earth :-)
Received on Tue 04 Dec 2007 02:28:58 PM PST