The Earth as its own nuclear magnetic resonance machine

[beatfrequency]

My physics buddy and I have been having a debate. I was claiming that even under the natural Earth's magnetic field that with good signal to noise ratio based on the radar systems scaled appropriately the top layers of the Earth could be seen. He claimed that the signal to noise ratio of the T1 and T2 echo reply would be too low. Is thermodynamic noise too great for this task even with adaptive noise cancelling technologies? We were studying the Na2+ ion for Earth Gauss levels of magnetic field and the NMR and ion cyclotron resonance frequencies and intensities.

Has anyone run the equations and what do you think? Is it possible?

 

[beatfrequency]

In a related note can it also be done with electron para-magnetic spin resonance imagining even on static electricity at Earth Gauss levels?

 

[f.wright]

I think your proposal is overly ambitious. For NMR and EPR to work you have to have a steady homogeneous B field over the resonant sample (or at least know how the B field varies over space). Take out your gaussmeter and walk around the lab and you will see that the Earth's magnetic field is not very homogeneous. Also, say you wanted to do NMR on a mountain. You would have to wrap a pickup coil around the mountain (with miles of wire) and attempt to detect a very small NMR signal at rf frequencies. This huge coil would have a very small Q factor. The only data you would get would be lighting crashes and the a.m. band talk shows. In EPR, the sample is placed in a high Q microwave resonant cavity and exposed to microwaves coupled to the cavity resonant modes. The sample is placed between the poles of a magnet and the intensity of the B field is varied until the sample absorbs the microwave energy and causes the resonance peak of the cavity to collapse. You need a high Q resonant cavity, a steady homogeneous magnetic field, and electromagnetic radiation at the appropriate frequency to do magnetic resonance.

 

[beatfrequency]

Could you use the ionosophere and Earth as the cavity? Let's say the B field is known precisely everywhere. I thought that at Earth Gauss levels (.5) that paramagnetic electron resonance is roughly 1.4 Mhz. NMR resonances would fall under 1000 Hertz (ELF) with simple ions. What if the coil was made of super conductor for a high Q?

 

[beatfrequency]

Also I thought I read somewhere that manipulation of the B field is preferable in the lab but it is not necessary to create the effect. The B field can remain constant and the resonator altered. I maybe confused.