John, you wrote,
"As I understand it, the only direct evidence Marvin Herndon presents is the changes in He-3 to He-4 ratios. What are other sources of He-3? You point out the articles that appeared in PNAS. Have you seen any that contradict them? (Eventually, I will probably sit down and read more on this subject.) "
You understand right (see also http://www.nuclearplanet.com/helium3_evidence.htm and the linked pdf PNAS document therein).
But there is
potential (not yet exploited) for similar direct evidence using, according to
Marvin, " Other ternary fission products, which should be sought and which
might be found in deep-source oceanic basalts, are shown in Table 3 ["Potential
in-core nuclear fission signatures in oceanic
basalts."]. All of the isotopes shown in Table 3, with the
exception of 10Be, are stable. Generally, light-element, ternary
fission products, if radioactive, have very short half-lives. A notable
exception, however, is 10Be, with a half-life of 1.5 X 106
years. Both 10Be and 9Be are produced by the georeactor
with an initial ratio 10Be/9Be = 6. Although a major
technological challenge, serious efforts should be made to find evidence of
nuclear fission produced beryllium in high 3He/4He oceanic
basalt samples and then to devise a means for using 10Be to obtain
helium time-of-formation data."
Marvin also includes Neon isotopes in his Table 3 list of "Potential in-core nuclear fission
signatures in oceanic basalts."
As for..... "I also wonder about Herndon's statement that the magnetic field is what prevents the atmosphere from being stripped from the Earth. Venus has practically no magnetic field, yet has an atmosphere. "
.........the statement about the atmosphere being stripped off was in fact Hollenbach's (according to the UPI article). I believe it to be true. Venus is different, because its far more volcanic, pumping huge amounts of gas into its thick atmosphere.
Also, its high temperature prevents it from storing CO2 in carbonate rocks and oceans (there aren't any).
Lastly, it was mentioned in one of the linked articles you referred to earlier, that "While solid core formation in Earth's interior maintains its dynamo to this day by virtue of the related 'stirring' of the molten core around it, Venus appears to either lack the necessary internal ingredients (chemical or physical) for solid core formation, or to have ceased such processes at an earlier time if they resulted in complete core solidification or arrested core solidification." ...to which I would add that its also possible that the Venusian georeactor is more powerful than earth's, preventing a solid core from forming at all ! (thus no "stirring of the molten core around it" and no geomagnetic field....)
The article adds that "It is also notable that Venus would not have maintained any remanent crustal magnetic fields from its proposed early period of dynamo activity because the temperatures in the crust are expected to be above the Curie point (below which such fields could persist in rocky materials)."
To my mind, there is much less uncertainty about the likelyhood of a georeactor, than there is about its link to the operation of the geomagnetic field. I think these two issues should probably be dealt with separately, in spite of the fact that periodic shutdowns appear to be a tempting explanation of the mechanism of geomagnetic pole reversals.
Hope this makes some sense.
Cheers,