Magnetic Field Reversal

[pwdrive]

I have just picked up on a post from a non radio related forum, basically the person concerned wants to buy an old dissused mine, he stressed that it needed to be a "walk in" type of mine ie: entrance via a walk in adit/portal.
Initally he did not specify his reasons for buying one, normally it might be for growing musherooms in or some other plant by artificial lighting (I think you know what I mean)
However the post has developed and the person has stated that it is for the storage of computer and magnetic storage media .
He has made a prediction the there will be a complete flip of the earths magnetic field in about a year or so and that the result of this will be a very large EMP that will knock out the grid systems and fry all magnetic storage media.
I do know that there is evidence of magnetic field reversal in the earths past history but I have no idea what different effects it would have if it were to occur now, apart from maybe having to turn my compass the other way round.
Anyone know?
Any thoughts. Note: it is his prediction not mine.

Lawrence.

[Joe]

I too have heard that the Earth's magnetic field periodically flips and, not only that, but it is over-due so to do.

As for the effect I've no idea and I can't see how being underground would help.

- Joe

[AlanBeckett]

http://en.wikipedia.org/wiki/Earth%27s_magnetic_field
The earth's magnetic field is pretty weak compared with what is easily generated electrically.
I don't see why a 'flip' should have any drastic effects, or why being underground would help.
Alan

[Geaney]

I agree, being underground won't help.

Here's a clip on the subject:

http://www.youtube.com/watch?v=wMq71euHBOs

or this from National Geographic:

http://news.nationalgeographic.com/news/...field.html

In any case I'd say the term 'flip' is perhaps not the best one to use since it seems this transition can take some time.

Cheers, John

[Skywave]

Time for a review of some basic Physics.

Consider a conductor, whose inductance = L Henries and that conductor being in a changing magnetic field whose rate of change of flux = dφ/dt: induced emf = -L.(dφ/dt). Now consider all the miles and miles of electrical conductors that weave their way in the Earth and on the surface of the Earth plus various chunks and lengths of metal that exist almost everywhere: L will accrue to a very large value. If the reversal of the Earth's magnetic field is rapid enough, dφ/dt becomes a large quantity. Note that although the Earth's magnetic field may be comparatively weak, it is the rate that it changes that is the essentially critical factor. Hence, the induced emf in those conductors could easily become enormous. The consequences will be truly horrific on a total global scale. Putting metallic items in a cave to protect them from such an event will be a complete waste of time, not that any of us will be around afterwards to argue the point.

I really don't want to think about this scenario anymore!

Al.

[Robert Darwent]

He has made a prediction the there will be a complete flip of the earths magnetic field in about a year or so and that the result of this will be a very large EMP that will knock out the grid systems and fry all magnetic storage media.

What utter rot! If it was April rather than August I would dismiss it as a 'fool's' prank.

The Earth's magnetic field has periodically reversed many tens of times (if not hundreds) during geological history. It is a slow process over many centuries where the field diminishes, changes polarity, then strengthens again. It does not cause an electromagnetic pulse (EMP) of any kind, it would have to occur virtually instantaneously to do so such as occurs with a thermo-nuclear explosion.

There has been recent evidence that the Earth's magnetic field has been weakening on a shorter timescale (over the last century or so) and predictions, if it continues on its current trend, that there will be virtually no detectable field by the end of this century. But it is far more likely to increase again before that happens as it is subject to minor variations over decades as well as long term cycles.

Even if the magnetic field was to disappear tomorrow, worrying about magnetic media surviving will be the least of anyone's concerns. The Earth's protective magnetosphere will have also disappeared and everything and everyone will be 'microwaved' by the solar wind and cosmic radiation! Hiding in the deepest mine will offer little protection in such a scenario.

Regards

[Skywave]

[The reversal of the Earth's magnetic field] is a slow process over many centuries where the field diminishes, changes polarity, then strengthens again.

I see: a slow process. Thank goodness for that! So references to the Earth's magnetic field 'flipping' is something of an exaggeration then.
Thank you Robert.

Al.

[pwdrive]

Gosh, I wasn't expecting any replies, but just to recapp I posted various replies to OP's question on that other forum, they pretty much tally up with what you guys have just said ie: an EMP by it's very wordly description means just that ie: a very short risetime/quick rate of change etc. Although the original posters idea is easy to snub the subject arising are very interesting.
Earth directed solar events as has been pointed out can have a considerable effect on electrical transmission systems on the planet, and have been well documented as have the effects on electromagnetic propagation which I am sure all of us radio guys are familiar with. metaliferrous deposits aside, the mag field below ground is more or less the same as on suface, after all as far as I know that is where it comes from.
Here is a link to the on going "discussion" home page, if you look for the latest forum posts you should find it ok if interested, you should be able to view without signing up, however if you are interested in things underground then feel free to sign up, it's free and no crap mail.

http://www.aditnow.co.uk/

Forgot to add: the title of the post is... buying an old mine....then scroll through to find it.

Lawrence.

[pwdrive]

He has made a prediction the there will be a complete flip of the earths magnetic field in about a year or so and that the result of this will be a very large EMP that will knock out the grid systems and fry all magnetic storage media.

What utter rot! If it was April rather than August I would dismiss it as a 'fool's' prank.

The Earth's magnetic field has periodically reversed many tens of times (if not hundreds) during geological history. It is a slow process over many centuries where the field diminishes, changes polarity, then strengthens again. It does not cause an electromagnetic pulse (EMP) of any kind, it would have to occur virtually instantaneously to do so such as occurs with a thermo-nuclear explosion.

There has been recent evidence that the Earth's magnetic field has been weakening on a shorter timescale (over the last century or so) and predictions, if it continues on its current trend, that there will be virtually no detectable field by the end of this century. But it is far more likely to increase again before that happens as it is subject to minor variations over decades as well as long term cycles.

Even if the magnetic field was to disappear tomorrow, worrying about magnetic media surviving will be the least of anyone's concerns. The Earth's protective magnetosphere will have also disappeared and everything and everyone will be 'microwaved' by the solar wind and cosmic radiation! Hiding in the deepest mine will offer little protection in such a scenario.

Regards

Good point on the magnetosphere scenario, I will make that known on that other forum, thanks.

Lawrence.

[ed731pdh]

There's a place in the South Atlantic, the South Atlantic Anomoly, that already has a weakening of the magnetic field: http://en.wikipedia.org/wiki/South_Atlantic_Anomaly