| The Earth's magnetic field has existed for at least 3 billion years with high and on average stable intensity, though with many fluctuations and reversals. One of the models, albeit rather controversial, proposed as the energy source of the Earth's magnetic field is a natural nuclear reactor inside the Earth's core [1] and [2]. This author maintains that this is the only model that generates sufficient power to energize the geo-magnetic field for 3 billion years. Even more, the reactor's ability to produce variable power levels including stops and restarts in its operations, provides a viable explanation, according to [2], for the random reversals of the geo-magnetic field that have been recorded numerous times during the Earth's history.; In this study, Kamioka Liquid scintillator Anti-Neutrino Detector (KamLAND) is used to set limits on the power of the putative geo-reactor. KamLAND is designed to detect anti-neutrinos from reactors around Japan, and thus can make a direct measurement of the anti-neutrino rates coming from the geo-reactor for the first time in history, if one exists. From measurements of bounds on the geo-reactor anti-neutrino rate, the thermal power of the geo-reactor may be estimated. Fortunately, the power reactor rate varies with time and this provides a powerful search tool.; Based on a total of 776 ton-year exposure of KamLAND to anti-neutrinos, the best fit for the geo-reactor thermal power is ( 5.9+6.4-5.9 ) TW. This result is more than 1sigma level above zero expected geo-reactor power, giving a hint for its existence. Also, this result is consistent with the model prediction of expected heat flow from the Earth's core of 3--10 TW. Although, 21 TW 90% C.L. upper limit for the geo-reactor is rather high, it is comparable to the lower limit for the overall expected radiogenic heat of 19--31 TW. The sum of radiogenic heat (19--31 TW) and reactor heat ( 5.9+6.4-5.9 ) TW is compatible with the direct heat flow measurements which are between 31 and 44 TW. |
