Re: gps after nagnetic field loss?

junkmail@xxxxxxxxxxx wrote:
On Tue, 31 Oct 2006 04:58:33 GMT, Sam Wormley <swormley1@xxxxxxxxx>
wrote:

matt weber wrote:

GPS could care about the earth's magnetic field. The GPS sats are in
orbits high enough that the field provides no shielding from the solar
wind anyway. GPS works by measuring the difference in the arrival time
of the signals.
GPS satellites are at 4 earth radii.

Earth's magnetosphere
http://en.wikipedia.org/wiki/Magnetosphere#

The magnetosphere of Earth is a region in space whose shape is primarily
determined by the distortion of Earth's internal magnetic field and by
solar wind plasma and the interplanetary magnetic field (IMF). In the
magnetosphere, a mix of free ions and electrons is held mainly by magnetic
and electric forces that are much stronger than gravity and collisions are
rare.

In spite of its name, the magnetosphere is quite non-spherical. On the
side facing the Sun, the distance to its boundary (which can vary) is
about 70,000 km (10-12 Earth radii or RE, where 1 RE=6371 km; unless
otherwise noted, all distances here are from the Earth's center). The
boundary of the magnetosphere ("magnetopause") is roughly bullet shaped,
about 15 RE abreast of Earth and on the night side (in the "magnetotail"
or "geotail") approaching a cylinder with a radius 20-25 RE. The tail
region stretches well past 200 RE, and the way it ends is not known. The
neutral gas envelope of Earth ("geocorona") continues to about 4-5 RE,
with diminishing density and minimal interaction with the plasmas of the
magnetosphere. So does the upwards extension of the ionosphere, known as
the plasmasphere.

If/when we lose the earth's magnetic field, then we're toast. The
earhth's magnetic field blocks alpha radiation from the sun and
deflects it towards the magnetic poles, leading to the infamous Van
Allen belts. Without the magnetic field, this alpha radiation would
bombard the earth, and the only beings that would survive would be
those that are protected, such as sea life and bacteria.

I suspect you meant protons and electrons making up the solar wind as
opposed to alpha articles (helium nuclei). The earth's atmosphere would
absorb the majority of the radiation. The earth's magnetic field has
weakened considerably in times past--there is no correlation with mass
extinction.

Mars is a different story--no magnetic field and very little atmosphere
leaving the surface of Mars bombarded with ionizing radiation.




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