Is it possible to have tidal currents in the Earth's molten mantle?

[Gannet]

Since the tectonic plates ride on the convection currents in the molten mantle, I was wondering if tidal effects could create currents in the molten mantle.

The reason I am asking I found this http://bowie.gsfc.nasa.gov/ggfc/tides/intro.html"
where it states:

The tidal braking in the Earth's rotation is actually caused primarily by friction in the oceans, where "friction" may refer to any number of physical mechanisms which have yet to be determined definitively. For example, bottom friction, induced by tidal currents flowing across the seabed, various kinds of wave breaking, and scattering of tidal waves into oceanic internal waves are all thought to play a role. For a recent overview of this subject, look up Walter Munk's paper "Once again: once again--tidal friction," published in Progress in Oceanography, vol. 40, pp. 7-36, 1997.

This made me wonder if there tidal currents in the molten mantle that the tidal friction with tectonic plates would be significantly greater than the tidal friction created by the oceans.

 

[Dr_Morbius]

The scientists at NASA are very qualified people and I am certain that they considered all possible sources of tidal friction. Therefore, since they said "tidal braking in the Earth's rotation is actually caused primarily by friction in the oceans" that this must be the case otherwise how embarrassing would it be if someone on some forum discovered something that they missed.

 

[Gannet]

The scientists at NASA are very qualified people and I am certain that they considered all possible sources of tidal friction...

Thanks for replying. I would hope your statement is true and not just "...the light is better here."

Since the tidal potential deforms the entire earth. It seems to me qualitatively that more of tidal potential would be dissipated in the solid Earth than in the ocean. However, the main stream believes

Most of the tidal energy dissipation is believed to occur in the oceans. It is still not entirely clear whether most of the dissipation occurs in shallow seas or in deep oceans.

from http://www.geo.ucalgary.ca/~wu/Goph681/EarthRotation.pdf"

 

[billiards]

Since the tectonic plates ride on the convection currents in the molten mantle, I was wondering if tidal effects could create currents in the molten mantle.

The reason I am asking I found this http://bowie.gsfc.nasa.gov/ggfc/tides/intro.html"
where it states:

This made me wonder if there tidal currents in the molten mantle that the tidal friction with tectonic plates would be significantly greater than the tidal friction created by the oceans.

This is not something I claim to know very much about.

With that caveat, it seems to me that the viscosity of the mantle is too high to permit dissipation by currents. However, I believe that some tidal energy is dissipated by heating the mantle.

 

[D H]

Since the tectonic plates ride on the convection currents in the molten mantle, I was wondering if tidal effects could create currents in the molten mantle.

First things first: What molten mantle? The Earth's mantle is a solid (it supports shear waves) that is capable of plastic flow over geological time spans.

The reason I am asking I found this http://bowie.gsfc.nasa.gov/ggfc/tides/intro.html"
where it states:

The tidal braking in the Earth's rotation is actually caused primarily by friction in the oceans

You missed the key word "primarily". They did not say "exclusively".

This made me wonder if there tidal currents in the molten mantle that the tidal friction with tectonic plates would be significantly greater than the tidal friction created by the oceans.

The key problem in your reasoning is your use of the term "molten mantle". Over very long time spans (geological time) the mantle appears to be plastic. Over very short time spans such as those resulting from tidal interactions, the mantle is better modeled as an elasto-rigid body with a small degree of anelasticity.

Just as the oceans are subject to tides from the Moon and the Sun (and to a lesser extent the other planets), so is the Earth itself. The same tidal forces that result in the ocean tides also affect the Earth as a whole. Google the terms "Earth tides" and "solid body tides" for more. The Earth tides are for the most part loss-free because the Earth as a whole is mostly elastic on the time scales of the tides (hours to decades). The small amount of anelasticity in the mantle will lead to some losses, but these are small compared to those resulting from the ocean tides.

 

[Gannet]

Thank you Billiards & D H for your comments

From Billiards

...it seems to me that the viscosity of the mantle is too high to permit dissipation by currents. However, I believe that some tidal energy is dissipated by heating the mantle.

The post-glacial bounce in 11,000 years indicates to me though highly viscous that flow does exist. Also, tidal heating to me indicate friction which indicate that there is an opposing force to movement. Maybe the solid Earth tidal bulging is inducing that movement.

From D H

You missed the key word "primarily". They did not say "exclusively".

I know it is not exclusively, I was challengining the word "primarily" which in my terminology means the #1 contributor. I have not found any paper yet that substantiate that claim.