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Author Topic: Do magnetic fields heat lunar oceans?  (Read 1488 times)

Offline chiralSPO

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Do magnetic fields heat lunar oceans?
« on: 13/03/2015 16:12:31 »
It appears that there may be liquid salty oceans on Europa, Callisto, Ganymede, Enceladus, and maybe more of the Jovian and Saturnian moons. It has been proposed that tidal friction is responsible for providing the heat to melt ice and keep it liquid.

Some of the evidence for salty liquid oceans is from analysis of the interactions of the moons with the magnetic fields of their respective planets. (The planet's magnetic field induces a current in the ocean, inducing an opposing magnetic field)

My questions are:
How much heat is likely produced by these induced currents? (Could it be comparable or even greater than the effects of tidal heating can we estimate an upper bound?)
Do the moon's orbits take them through significantly different magnetic potentials such that there is variable (or even alternating) current?


 

Offline chiralSPO

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Re: Do magnetic fields heat lunar oceans?
« Reply #1 on: 13/03/2015 16:19:55 »
I should have done a google search *before* I posted the question. Apparently there is some Joule heating predicted for Enceladus. I have provided the title and abstract of a paper published in 2011 in the Journal of Geophysical Research: Planets. (apologies for the formatting...)

"Joule heating of the south polar terrain on Enceladus
K. P. Hand, K. K. Khurana, and C. F. Chyba

Received 12 November 2010; revised 1 February 2011; accepted 13 February 2011; published 27 April 2011.

Abstract: We report that Joule heating in Enceladus, resulting from the interaction of
Enceladus with Saturn’s magnetic field, may account for 150 kW to 52 MW of power
through Enceladus. Electric currents passing through subsurface channels of low salinity
and just a few kilometers in depth could supply a source of power to the south polar
terrain, providing a small but previously unaccounted for contribution to the observed
heat flux and plume activity. Studies of the electrical heating of Jupiter’s moon Europa
have concluded that electricity is a negligible heating source since no connection between
the conductive subsurface and Alfvén currents has been observed. Here we show that,
contrary to results for the Jupiter system, electrical heating may be a source of internal
energy for Enceladus, contributing to localized heating, production of water vapor, and the
persistence of the “tiger stripes.” This contribution is of order 0.001–0.25% of the total
observed heat flux, and thus, Joule heating cannot explain the total south polar terrain
heat anomaly. The exclusion of salt ions during refreezing serves to enhance volumetric
Joule heating and could extend the lifetime of liquid water fractures in the south
polar terrain."
 

Offline evan_au

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Re: Do magnetic fields heat lunar oceans?
« Reply #2 on: 13/03/2015 21:39:32 »
Quote
Do magnetic fields heat lunar oceans?
Pedantic comment: "Lunar" is derived from Latin, and refers specifically to Earth's Moon. There are "seas" (Maria) on Earth's Moon, but we now know that they are basaltic flows, which won't conduct electricity to any significant degree.

Since the Romans didn't know of any other moons, they didn't have a word for them in Latin.

Galileo was the first to see other moons circling Jupiter, through his telescope. However, he started writing in Italian, rather than Latin.

I think the generic term is "moon" in lower case; "natural satellite" is a mouthful, and too easily confused with the "artificial satellites" that make the news from time to time....
 

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Re: Do magnetic fields heat lunar oceans?
« Reply #2 on: 13/03/2015 21:39:32 »

 

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