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dmill120
2006-Oct-21, 03:50 AM
HEllo people!
I have a question that I hope someone hear can answer.
From what I understand the Earth has had several Magnetic reversals in the past that have been confirmed from studying Iron Rich Lava flows or other geological samples, and there is evidence that our field has been decaying over time, http://en.wikipedia.org/wiki/Earth%27s_magnetic_field#Magnetic_field_decay
is there any Geologic or, Archeologic evidence, that might suggest that our Atmosphere, or water content has been altered during these Magnetic Pole reversals from the the Solar wind, or Radiation, since it appears to take quite some time for this transition.

And does the evidence suggest that every time we start to go through such a reversal, Our Magnetic field is weakened?
I am wondering how the Solar wind has effected Earth in the past during such reversals, and if analyzing Rock samples from these periods has shown a difference in Gaseous traces or water content?
Dennis:)

yuzuha
2006-Oct-21, 05:41 AM
Cancer rate would increase a few percent, some satellites would get knocked out from radiation damage or atmospheric drag (already happening over the South Atlantic anomaly http://heasarc.gsfc.nasa.gov/docs/rosat/gallery/misc_saad.html where part of the core has already reversed), and you'd see the aurora in odd places. Scientists don't think it will have too much effect on the atmosphere since reversals don't last very long in geological terms (one flow recorded a magnetic shift of 6 degrees per day). Now if the earth lost its field, a few million years of solar wind might be noticable. http://www.pbs.org/wgbh/nova/magnetic/

Kaptain K
2006-Oct-21, 04:36 PM
A common misconception is that when the poles reverse, the field decreases to zero and then increases again. This is incorrect. The dipole field goes to zero, but higher order (quadropole, octopole, etc.) remain, so the Earth is not completely defenseless.

BigDon
2006-Oct-21, 05:18 PM
Thanks Kaptain, I did not know that. Which is why we're both here I guess.

tusenfem
2006-Oct-21, 06:54 PM
Indeed, Captain.
And the fun part is for the people living in Los Angeles is that they will have the auroras! And it will not be a hollywood production.

dmill120
2006-Oct-21, 06:59 PM
Thanks Guys!
I Couldnt find any Info ,as to whether we would lose our magnetic field during a Reversal or if it has been recorded somehow Geologically in the past.
I knew someone here could help answer this one for me!
you guys rock!
Dennis:)

Dragon Star
2006-Oct-21, 07:03 PM
A common misconception is that when the poles reverse, the field decreases to zero and then increases again. This is incorrect. The dipole field goes to zero, but higher order (quadropole, octopole, etc.) remain, so the Earth is not completely defenseless.

Well that was unexpected. Interesting, thanks.

trinitree88
2006-Oct-21, 08:21 PM
Well that was unexpected. Interesting, thanks.

Kaptain...add me to that list. Interesting. Pete.

yuzuha
2006-Oct-22, 03:50 AM
http://geomag.usgs.gov/movies/ has some maps/movies showing the field to the present. In the core field movie you can see that multiple south poles are forming and merging in the South Atlantic (the North pole is actually a magnetic South pole, which is why the North end of a compass needle points to it). This is drastically weakening the overall field strength over that area as they oppose the overall North magnetic field in the region. Wanderign quadra and octapole etc. fields are unstable and probably won't support the Van Allen belts and would probably allow the solar wind to have an effect on the atmosphere (as has already begun to happen in the S.A.), but other than confusing migration patterns, a reversal will probably have more of an effect on our technology (especially satellite communications etc.) and make it easier for coronal mass ejections to screw with our power grids than anything.

BISMARCK
2006-Oct-23, 10:32 PM
This raises a question for me. Electric current runs from negative to positive, which is why, I'm told, Electrical engineers reverse their terminology.

So, when people refer to the Earth's magnetic "North" Pole actually being a "South" pole, does this mean that magnetism has a similar absolute frame of reference that electricity does? Obviously I know the two are related, but I always thought of magnetic poles as being defined only in terms of "this one is like that one" or "this one is different than that one." I never thought of "north" and "south" as actually having a real, absolute qualitative difference.

yuzuha
2006-Oct-24, 12:55 AM
The North pole of a magnet or compass needle will point towards the geographic North pole of the earth because the earth has a South magnetic pole near the geographic North pole... we call it "magnetic North" but that is magnetically determining geographic North which is actually near the earth's magnetic South pole (remember, opposites attract and likes repel)

yuzuha
2006-Oct-24, 01:25 AM
If I remember correctly, if you pick up a coil of wire (electromagnet) in your left hand and curl your fingers around it in the direction of electron flow, from negative (-) to positive (+), your thumb will point toward the North pole of the electromagnet... if you're and engineer using conventional current (+ to -) use your right hand.

Yeah, found a page that might help http://www.eatonelectrical.com/unsecure/html/101basics/Module02/Output/ACVoltage.html

dmill120
2006-Oct-24, 03:31 AM
Hi Folks,
I had to learn basic electronics way back in the early seventies since I was A Radar technician for the Army's Early warning air defense system, the Hawk and, another longer range system the Hercules ,
but way back then We had transistor tube technology except for, our Identification friend or foe system, this was a more modern circuit board slot technology with transistors, anyway, back then there were two theories for electricity the (conventional) pos to neg, and the (electron theory) which is the neg to pos direction, but they also called this the (electron hole theory). in either case it really doesnt change the basic principle of electronics, Coulumbs law the law of inductance, Henry's Law or the laws of capacitance and resistance in either an AC or DC circuit.
any coil resists a sudden change induced by a moving magnetic field,or potential, this resistance produces a current in the coil, the motion of a magnet back and forth within a coil will produce this current. coils are employed typically in a Tank Circuit for DC rectification or a Resonance Circuit , for Oscillation, this is an old circuit design, nowadays they use a bridge rectifier or Diodes and Capacitors intead of this old design.
note that there is no polarity indicated in this circuit example, here is a link
http://www.allaboutcircuits.com/vol_2/chpt_6/2.html
Dennis :)