BigGiraffe
Topic Author
Posts: 256
Joined: Sat Jan 29, 2000 7:58 am

Magnetic North

Sun Apr 02, 2000 10:00 am

Today I learned that the magnetic pole of the Earth drifts around over time, and so some runways periodically get renamed (i.e., was 27L, now 28L) because the compass reads differently than it did a few years ago. How many years does this drift pattern take to complete a cycle? Or is it a recurring cycle?

Thanks,
BigGiraffe
 
fr8tdog
Posts: 120
Joined: Wed Feb 16, 2000 4:25 pm

RE: Magnetic North

Sun Apr 02, 2000 3:24 pm

Runway numbers are changed as needed, I think the avg. is around 10-11yrs. this depends on the geographic location.
 
aaron atp
Posts: 517
Joined: Sun Mar 19, 2000 1:17 pm

RE: Magnetic North

Sun Apr 02, 2000 4:03 pm

I believe the trend is about a degree every 50-60 years... depending on where you are located.If you have access to a nautical chart, it will have annual rate of change for that area inside each compass rose... I always tell people that the change will be insignificant in your lifetime, so don't worry about it... Apparently it takes several millenia for the magnetic poles to switch...

Scientist have studied iron deposits around the earth in different stratas of the crust, and have indeed found evidence that this has been a recurring trend.

I believe the current trend is the pole is moving underneath the general area of 90W in a northerly direction right now.... at about 15 kilometers per year.





Some people instinctively feel that this movement is a "bad" thing, but it certainly is not... the magnetic compass is fast becoming a relic of the past... It is my opinion that runways should should be renamed to true headings as soon as WAAS is implemented....



 
BigGiraffe
Topic Author
Posts: 256
Joined: Sat Jan 29, 2000 7:58 am

RE: Magnetic North

Mon Apr 03, 2000 1:23 am

So the movement is towards the south pole? I had pictured it as a circular pattern somewhere up north. Interesting. I wonder why it is moving?
 
aaron atp
Posts: 517
Joined: Sun Mar 19, 2000 1:17 pm

It Is Moving North Tight Now

Mon Apr 03, 2000 3:04 am

I explicitly said in my previous message that the current trend is northerly movement.

However, it will one day reach it's apogee and begin moving south again...

look at this picture again:


it is moving almost due north underneath canada right now....

I also first believed that it moved in a line following something that looks like the arctic circle, but then I was proved wrong, so I accepted the obvious...

flow of eltrical currents in the earth's core is to blame...

check out:
http://www.geolab.nrcan.gc.ca/geomag/e_nmpole.html


aaron
 
Samurai 777
Posts: 2000
Joined: Thu Jan 27, 2000 2:56 pm

RE: Shifting Magnetic Pole And Reversals

Mon Apr 03, 2000 3:40 am

The shifting of the magnetic poles are indeed caused by electrical currents running throuh Earth's outer core and lower mantle. These currents fluctuate probably due to the sloshing of the mantle.

A potentially serious concern, especially for aircraft navigation systems, is that we are overdue for another magnetic field reversal(in terms of strength and direction of current), as the magnetic field has been switching every 700,000 years for last 2-3 million years. There is an awful lot of evidence of reversals, especially in volcanic rocks, which contain iron deposits.

Currently, the north magnetic pole is stronger than the south magnetic pole(sitting in Antarctica). A reversal would be a problem because during that time, the magnetic field is temporarily weakened greatly and compasses or navigational aids that rely on compasses would be rendered useless worldwide. Aircraft, both commercial and military, rely on navigation systems greatly. This will be a problem, unless a greater emphasis is placed on satellite navigation systems, like the GPS. The GPS(Global Positioning System) is a network of at least 22 satellites currently in orbit worldwide. If a commercial aircraft used this, only 3 or 4 satellites are used to triangulate the position, which is accurate within 100 metres(330 ft). The military version is about 10 times more accurate.

Also, with the magnetic field weakened during a reversal, there is the concern of greater exposure to cosmic radiation and charged particles from the sun at higher altitudes, not only to astronauts, but also pilots and passengers who fly frequently enough. Although the greater exposure wouldn't be that deadly, cancer is more of a problem. Even now, the region around the North Magnetic pole is a concern to such people on polar routes, because there is less of the magnetic field protecting Earth from the cosmic radiation.

A reversal would probably take about a century or perhaps over a thousand years, but little is known about them, as a reversal has never happened in recorded history.
 
BigGiraffe
Topic Author
Posts: 256
Joined: Sat Jan 29, 2000 7:58 am

RE: Magnetic North

Mon Apr 03, 2000 8:10 am

Sorry. When I first read Aaron's post I got hung up on the words "it takes several millenia for the magnetic poles to switch", missing the word "northerly" in the later sentence.

Seems to me having the magnetic pole moving north to coincide with the north pole is a good thing. But as you all pointed out, it moves so slowly it really doesn't matter.

Thanks,
BigGiraffe

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos