Talk:Earth's magnetic field

Contents

1 Magnetic field weakening 2 Error 3 Dynamo theory 4 Telluric currents

Magnetic field weakening

This is scaring me. If the Earth's magnetic field is getting weaker because of a possible reversal in progress, does this mean that all life on Earth could be extinguished? Denelson83 19:32, 16 Jan 2004 (UTC)

No, Earth's magnetic field has reversed hundreds of times in the geologically recent past without even causing mass extinctions, let alone exquinguishing all life. IIRC, the main effects will be shorter satellite lifespan (the magnetic field protects Earth orbit from radiation) and auroras that will be visible all over the world. The first is an annoying economic problem, and the second should be downright pretty. Earth's atmosphere is sufficient to block harmful radiation all on its own. Bryan 02:02, 16 Mar 2004 (UTC)

But I was told that if the Earth's magnetic field is absent, then the solar wind itself would have a chance to start eroding the Earth's atmosphere. Denelson83 03:42, 16 Mar 2004 (UTC)

It'd start, but the field would only be down for a few years and the amount of erosion that could happen in that period of time is negligible. Bryan 03:52, 18 Mar 2004 (UTC)

You should be more worried about global warming and ozone depletion. Lirath Q. Pynnor

I don't know if the solar wind would "erode" Earth's atmosphere; it is more likely Earth would gain a little hydrogen from the solar wind. The amounts involved would be tiny. The fact that we exist is an indication that there has not been a fatal problem during the many previous reversals. And the ozone layer would probably produce more shielding because it would get thicker, with stronger magnetic fields being induced within the ionosphere. We'll have to update Wikipedia then. (SEWilco 05:36, 14 Mar 2005 (UTC))

The net effect is definitely to deplete the atmosphere, but even if the magnetic field just quit entirely, the relevant time scale is a few billion years, so nothing to worry about. I wouldn't expect the ozone layer to change much because it is dominated by UV effects not energetic particles. Dragons flight 05:57, Mar 14, 2005 (UTC)

Error

I believe it is incorrect to say that the earth's magnetic field began weakening 150 years ago.

It was 150 years ago that regular measurements of the earth's magnetic field and over the last 150 years there has been a continual drop in the strength of the field totally 10%.

Without measurements or some other evidence, we cannot say anything about the strength of the earth's magnetic field prior to 150 years ago.

Saying that it started to drop 150 years ago suggests that the field was steady or increasing up until 150 years ago and suddenly went into decline 150 years ago. However, the figure of 150 years ago is not the time whe it started to decline but the time when regular measurements were first taken and hence when it became possible to ***notice*** the decline.

A more correct statement would be: In the last 150 years, since regular measurements of the strength of the earth's magnetic field began to be recorded, the strength of the earth's magnetic field has dropped by about 10 percent.

I don't know when the Earth's field began it's current decline, but I do know that there are abundant measurements of paleointensity based on the remnant magnetization in lavas. Lavas lock in the magnetic field direction and intensity at the time when they solidified. I forget at what point that record shows the current decline beginning but I do remember that the highest intensity in the last several thousand years occured circa 1 AD (give or take a hundred years). Dragons flight 08:19, Dec 6, 2004 (UTC)

I included a paleogeomagnetic graph that gives an idea of how much the field strength has varied (stronger and weaker). Feel free to add encyclopedic explanations. (SEWilco 17:07, 14 Mar 2005 (UTC))

Dynamo theory

The text needs— for well-meaning simpletons like me— just the briefest characterization of dynamo theory as it relates to generation of the Earth's magnetic field, to make the picture more complete. A paragraph headied Main article: dynamo theory. is one well-tried way to do this. --Wetman 08:22, 14 Mar 2005 (UTC)

Telluric currents

You contradict yourselves here as when I looked up the Earth's Magnetic field,it stated that it was created from telluric currents, however when you look up telluric currents it states that these are effected by the earths magnetic field... So what came first the chicken or the egg? This isnt the only web site to make this same contradiction, which makes me wonder which is true?