This is not a question about conceding anything, but about education. The crucial point is that Th/U/K atoms by themselves decay spontaneously. A single U atom in empty space would all by itself some day decay. This is not what I would call a ‘reactor’. In a reactor, things are so arranged [either by us or by Nature] that the decay of one atom triggers the decay of other atoms ['before its time'] which then trigger the decay of still other atoms, etc, so the decays are not independent [that is what I meant by 'coordinated']. This also happens in an atomic bomb [and we don't really want that], so there are two more elements needed, namely a ‘moderator’ that will slow down the neutrons released to enhance the chain reaction and ‘control rods’ to stop or slow the reaction as we wish. In natural reactors, water plays the role of moderator and control rods are provided by the rock matrix in which the atoms are embedded. Such natural reactors are very rare and do not play any role in heating the Earth and, BTW, cannot any longer exist as the U235 needed for them to work has decayed so much that even chemically pure Uranium does not contain enough U235 for fission to work. So only billions of year ago could [and did] natural reactors exist here and there.

And finally, as you point out, the heat flow from the interior is totally insignificant.

I see.

Then at what point would you concede that a fuzzy collection of decaying Th/U/K atoms around the centre of the Earth might be construed to be a ‘nuclear reactor’?

Perhaps the word ‘coordinated’ is the key. What happens when it isn’t coordinated, when it isn’t planned?

From what I know about uncoordinated, unplanned processes – like the orbit of the Earth around the Sun – there is always a cyclicity about them. The uncoordinated and unplanned Sun, as you well know (far better than I do) also has its cyclicities. Why should we suppose that the Earth beneath our feet is unchangingly regular?

I suspect that I may be pursuing a lost cause here, because the the 0.075 W/m^2 terrestrial surface heat loss from below pales into pallid insignificance beneath the majestic Sun above.

But I like pursuing lost causes.

‘Up to date info’ is a reference to latest data from Ulysses, Pioneer and Voyager. For the wave issue, it is not possible to say if it is relevant or not unless it is thoroughly researched.
Charges travelling from the same direction will not short or collide in presence of magnetic field (in vacuum space)! Hence, “In solar wind and coronal plasmas the mean-free-path is enormous, so collisions play no role”.
Tutorial does say “We might expect variations in the electric potential along the magnetic field but no detectable variation in charge neutrality.”
Electric potential difference in a conductive medium is a result of an electric current flow.
Definitely “no change in neutrality” nQ2 = – nQ1 but I1= SnQ1* v1 , I2= SnQ2 * v2, and I=I1+I2 = SnQ1*(v1-v2) electric current through cross section S due to the velocity difference so “We might expect variations in the electric potential along the magnetic field”.
I believe that “horse manure per cubic meter” is highly praised by market gardeners. Thank you again and Good night.

Some, yes, but the most is coming from two sources: 1) the high pressure [when you compress things they get hot], and 2) left-over heat from the formation of the Earth.

Do you not count radioactive decay of Th, U, and K as constituting a ‘nuclear reactor’ because it’s too dispersed? According to one source:

The present-day heat flow through the surface of the Earth is consistent with energy sources in the interior, including secular cooling, the gravitational contraction associated with cooling, and decline of radioactive abundances.

It estimates [Table 1b] the radiogenic component of global heat flow at 24-36 terawatts out of a total of 39-66 terawatts. i.e. about half. 39 terawatts works out at an average global surface heat flow of about 0.075 Watts/m^2. Most of the radiogenic heat is suggested to come from the lower mantle.

New one to me, I had to look it up in a phrase book, but any transgression I let go by my personal ‘magnetosphere’ at a speed of SW, with no reconnection, unless I find it personally attractive (e.g. ‘cyclomaniac’ or ‘man of superior ignorance’).
Back to the science; the tutorial on solar wind is very useful and sufficiently informative, but could do with more of up to date info. I am surprised that none of the articles on SW I have come across, have considered the electron’s wave property (lambda=h/mv, ignoring the relativistic part), but always purely as a particle. Have to look into that one. Anything you know of ?

It is generally accepted in underground mining industry that 50 feet will do the trick. 100 feet if you want to be really picky.
I haven’t been in a mine yet that within 50 ft of the surface (horizontal or vertical) you were not confronted with the underground environment.
It could be 10 below or 110 above outside, and it won’t matter. You are at rock temperature.

vukcevic (01:15:53) :
“Interesting link, confirms that” the plasma is neutral.
re probability: p=k/n of equally probable and independent events. A short course of probability would do you good.

Particle velocity distributions are highly anisotropic in the solar wind because of its low density. Here http://spc.igpp.ucla.edu/ssc/tutorial/solwind_magsphere_tutorial.pdf is a good tutorial on that. I cite from it [page9]: “A paradox is introduced by this difference in velocity that arises because in the corona the ions and electrons have similar temperatures but very dissimilar masses. In a collisionless gas, like the solar wind over most of its transit from the sun, charged particles do not leave their magnetic field lines. They also maintain quasi charge-neutrality. How can they do this if they are not traveling at the same speed? The answer is trivial if the source regions on the sun are constant in time so that the flux of electrons and ions at the base of a field line is constant. The density is always the same and it does not matter if the protons and ions stream relative to each other along the field. If the solar wind production rate varies in time and the ion density along a flux tube varies with distance, then the electrons have to slow down as they pass through dense regions and then speed up in rarefied regions. This occurs because when there is an over abundance of ions there will be a polarization electric field that attracts the electrons to that region. In regions of under dense ions the electrons will be expelled by the excess negative charge. As a result, charge imbalances are minimal in the solar wind despite the speed differences and time variations. We might expect variations in the electric potential along the magnetic field but no detectable variation in charge neutrality.”

idlex (02:42:51) :
So where’s all that heat being generated inside the Earth? The crust rather than the core?
Some, yes, but the most is coming from two sources: 1) the high pressure [when you compress things they get hot], and 2) left-over heat from the formation of the Earth.

Thanks Leif.

So where’s all that heat being generated inside the Earth? The crust rather than the core?

rbateman: And we should be scientific about that, idflex, and start keeping record worldwide of rock temperature.

So every surface station should have an accompanying undersurface station?
And would we just measure temperature? Could we not also measure pressure? Use gps to measure ground speed? Is there an undersurface analogue of atmospheric humidity?

There’d be the same possibilities of heat island effects. If the air above NYC is several degrees higher than in sorrounding places, perhaps the earth beneath it is also several degrees higher too? How far down do you have to go to minimize the surface effects? Surface stations stand on legs a metre or two high. The undersurface stations might need ‘legs’ (pointing downwards) a kilometre long. And then we’s start thinking of hills and mountains as being transient clouds on the surface of the undersurface weather machine, in which everything happens very, very slowly.

In this manner we could scare the wits out of ourselves in entirely new ways.