# Earth's magnetic field

1. Sep 24, 2004

### drag

Greetings !

I'd like to know the approximate altitude above the equator
where the Earth's magnetic field has a peak value and what is
that value (assuming approximate surface value there is 0.3 Gauss).

Also, I'd appreciate any links including Earth's magnetic field
maps/simulators at and aspecialy above the surface (in LEO for example).

Thanks.

Live long and prosper.

2. Sep 24, 2004

### krab

The magnetic field decreases as elevation increases. There is no peak, unless you are talking subterranean.

3. Sep 25, 2004

### drag

I don't think that's the case, you don't expect the greatest
magnetic flux right near the external surface of a coil for example, do you ?
Also, from the rough field line plots I've seen here and there
it looks like it should be at some distance.

Peace and long life.

4. Sep 25, 2004

### Tide

The greatest flux will be near the poles. That's why we have the auroras at high latitudes. Earth's magnetic field is essentially a dipole field which varies inversely with the cube of the distance from the dipole. (Of course as you get closer to the center of the Earth the structure of the field becomes more complicated.)

5. Sep 25, 2004

### drag

Thanks. But, like I said, I'm more intrested in the equator.

6. Sep 25, 2004

### Tide

7. Sep 25, 2004

### krab

The surface of the earth does not function as a coil. In fact, the main source of the magnetic field is a long ways under you feet; it's in the (liquid) outer core. In 1838, Carl Friedrich Gauss proved 95% of Earth's magnetic field is internal, 5% external.
http://geophysics.ou.edu/solid_earth/notes/mag_earth/earth.htm

8. Sep 25, 2004