What are they? Where are they found? I think I remember hearing that they exist in the ocean, but anyone know?
Our military uses Magnetic Anomaly Detectors, which find perturbations in the earth’s magnetic field caused by large metallic bodies. Of course, the only reason to go to all this trouble is to find the ones you can’t see with your eyes or with radar - i.e., submarines.
The MADs are used on airplanes and helicopters. I think they lower them on a tether while they fly around, to get the MAD away from the plane, which has its own magnetic distortions.
Assuming the OP is asking about magnetica anamoly detectors (MADs) then CurtC is correct. See this link on the P-3 Orion for one of our military’s sub hunting planes. Scroll to the bottom of the linked page for photos and notice the long ‘boom’ (for lack of a better word) to see the Orion’s MAD. Other aircraft carry them as well but the Orion’s is perhaps the most obvious. As already mentioned the sole purpose for this is to detect submerged submarines.
If the OP is asking about the earth’s overall magnetic field then note that the field is by no means smooth. From a macro perspective it may be considered smooth but the magnetic field shows variations all over the place on a more local scale. This page has some detail and maps of the earth’s magnetic field if you’re interested.
Hey whack-a mole
Thanks for posting the P3 link. I worked on 2 of the detection systems back in the 60’s and early 70’s. The sonobouy systems were used ,as the name implys sono=sound= to listen for the engines. Today they may be diferent.
The Mad equipment was a system consisting of the head, an electro mechanical devise consisting of 3 gimbals which powered the element which consisted of 4 coils which was positioned 90 degrees to a set of 8 IIRC coils. This actually did the detecting.
Muldoon. the earth consists of many magnetic fields. When they are changed an anomally occurs. Magnetic anomally detection simply means change in magnetism .The MAD equipment detects things like change in the earths magnetic field caused by a submarine, mine, your car stopping at a controlled stop light.
Mad equipment is also used in earthquake detection.