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Ocean Currents Proposed As Cause of Magnetic Field
pjt33 notes a recently published paper proposing that ocean currents could account for Earth's magnetic field. The wrteup appears on the Institute of Physics site; the IOP is co-owner, with the German Physical Society, of the open-access journal in which the paper appears. This reader adds, "The currently predominant theory is that the cause of Earth's magnetic field is molten iron flowing in the outer core. There is at present no direct evidence for either theory." "Professor Gregory Ryskin from the School of Engineering and Applied Science at Northwestern University in Illinois, US, has defied the long-standing convention by applying equations from magnetohydrodynamics to our oceans' salt water (which conducts electricity) and found that the long-term changes (the secular variation) in the Earth's main magnetic field are possibly induced by our oceans' circulation."
The Slashdot summary is totally wrong.
From the abstract of the paper: "I propose a different mechanism of secular variation: ocean water [...] as it flows through the Earth's main field may [...] manifest itself globally as secular variation."
Meaning: There is a major magnetic field that comes from the molten core. However, certain variations that are as yet unexplained may not result from core phenomena, but from the ocean currents.
I find this much more believable than the swill in the slashdot summary.
That's correct. According to their theory, moons like Europa should have a rather strong magnetosphere.
Europa is believed to have a warm, salty ocean under the ice crust. And yet, it shows only slight inducted magnetic field from Jupiter. Contrast that with Ganymede, the only moon with its own magnetosphere and a liquid iron core. Satellite photos dont show very much (or any) water on its surface.
Hmm.
Because the other theory hasn't been tested, and might be wrong.
The point is that the chances that each celestial body's magnetic field is due to a unique generator are... Well, let's say that that is not what we typical see in scientific history. Similar effects are generated by similar causes, especially at planetary scales.
(I see that I've been misled by the summary, as usual. Yes, I should RTFA. But the editors should fucking WTFS in a manner resembling responsible journalism. Could currents in the oceans modulate the magnetic field? Worth investigation, I think.)
Mercury has a magnetic field, which quite surprised planetary scientists when it was first discovered by MAriner 10, as the prevailing theory at the time was that Mercury's small size would have led to its core solidifying by now and stopping the dynamo that generated the field.
There's obviously a lot we don't know about planetary magentic fields, and I wouldn't want to judge the entire theory just by something I read on Slashdot, but I find it hard to understand how oceanic currents could account for Earth's magnetic field but not for Mercury's.
The paper does not say that ocean currents cause the magnetic field. It hypothesizes that ocean currents cause secular variations in the magnetic field.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
No, the poles already reversed once in theory http://en.wikipedia.org/wiki/Earth's_magnetic_field, and are likely to keep reversing, though none of us will be around to find out.
No, the poles already reversed once in theory http://en.wikipedia.org/wiki/Earth's_magnetic_field, and are likely to keep reversing, though none of us will be around to find out.
If you do some non-wiki research, you will find out that Earth's magnetic field has reversed many times over the eons. We're overdue now by several thousand years. This Global Warming may be just another indicator that such a change is imminent.
Hundreds if not thousands of direction changes are documented, back into the Triassic at least and possibly into the Late Palaeozoic. There are sufficient that, in more recent times (Cretaceous onwards) the reversal record has been used as a tool for correlation. (Such work may go back further into the geological record ; I've certainly seen it used in Cretaceous mudrock sequences as a petrophysical indicator that can be measured faster and with less skilful operators than other techniques like palynology.)
For certain values of "overdue" ; the distribution of durations between reversal events seems to be essentially random, and since we're over the average duration between reversals, then one could meaningfully "expect" a reversal sooner rather than later. But once you start looking at the statistics, you have to accept that, if the model is accurate, then the probability of a reversal in the next thousand years (say), is the same as the probability of a reversal in the first thousand years after the last reversal. It's the same logic as tossing coins - if you get ten heads in a row, the probability of your next toss being a head is still 1/2, even if the probability of getting 11 heads in a row is 1/2048. Random variables - love 'em or hate 'em, but you can't predict 'em.
That said, outside the statistical description of the record, the physical models suggest that some events seen at the moment (decreasing field strength ; regional anomalies) may be precursors to a reversal.
Has someone been claiming global warming to be related to magnetic field strength? Whooo, can I get a smoke of that? Sounds like good gear.
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