Superconducting sensor could detect submarines by the magnetic disturbance of their wake

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The Debye effect could be used hunt submarines using the magnetic signatures of their wakes. Seawater is salty, full of ions of sodium and chlorine. Because those ions have different masses, any nudge—such as a passing submarine—moves some farther than others. Each ion carries an electric charge, and the movement of those charges produces a magnetic field.

Currently submarines rely on stealth to do their jobs, whether that is sinking enemy ships or hiding nuclear-tipped missiles beneath the ocean. The traditional way of hunting them is with sonar. Modern sonar is extremely sensitive. But modern submarines are very quiet, and neither side has gained a definitive upper hand.

There are other options. Submarine-spotting aircraft carry “magnetic anomaly detectors” (MAD) which pick up disturbances in the Earth’s magnetic field caused by a submarine’s metal hull. Those disturbances are tiny, which means MAD is only useful at ranges of a few hundred meters.

Cortana Corporation and the US navy will not discuss exactly what they are up to. But it is likely that the technique can only detect certain submarine movements in some situations. Submarines produce many different types of wake. As well as the familiar V-shaped wake they leave underwater disturbances known as “internal waves”, flat swirls called “pancake eddies” and miniature vortices which spin off from fins and control surfaces. These all depend not only on speed and depth but also on the submarine’s hydrodynamics (the underwater version of aerodynamics).

Work done in Russia, whose navy has long been interested in alternatives to sonar, suggests the Debye effect can be turned into something quite potent. In 1990, two contributors to the Soviet military magazine Naval Collection wrote that “as a consequence of the great extent of the wake, it is easier to detect this anomaly than the magnetic anomaly due to the metallic hull of the submarine.” That suggests that a well-tuned Debye detector might be able to pick up a trail from several kilometers back and follow it to find the submarine. Russia’s claims in this area have long been regarded in the West as exaggerated. The new American interest suggests they might not have been.

Things are likely to get easier, too: a new generation of high-tech magnetic sensors based on machines called SQUIDs—“superconducting quantum interference devices”—should be more sensitive than existing ones

Aquilinefocus blog reviewed alternative methods of submarine detection back in 2010. This included the debye effect and other Russian methods.

Falkenhagen Effect. This is the increase in conductivity of an electrolyte solution, such as an ocean, when the applied voltage has a very high frequency is known as Debye-Falkenhagen effect

SOURCES- Economist, wikipedia, aquilinefocus