No other manifestation of Earth has been as seemingly inexplicable as the Earth’s magnetic field. Albert Einstein is said to have considered its origin one of the most important unsolved problems in physics. More than a thousand years ago, individuals in China set afloat in bowls of water tiny slivers of loadstone, the mineral now called magnetite, and discovered that the slivers quickly assumed a preferred direction. That observation led to the development of the magnetic compass. In 1600, William Gilbert, shown at right, published De Magnete, based upon his extensive collection of magnetic measurements from around the globe, which showed that the Earth itself is like a giant magnet, rather than the magnetism arising from an extraterrestrial source as supposed by others [1]. In 1838, the mathematical genius, Johann Carl Friedrich Gauss, proved that the Earth’s magnetism source is at, or very near, the center of the Earth [2]. The Earth acts like a giant magnet with a magnetic field extending into interplanetary space, shielding the planet by deflecting charged particles of the solar wind, as illustrated at right, but it is not a permanent magnet. Inside Earth is too hot (above the Curie point) for a permanent magnet to remain magnetized. Moreover, the Earth’s magnetic field must continuously be fed with energy; otherwise its interactions with the solar wind and with matter in the Earth would cause it to decay and eventually disappear. Thus, there must exist at or near the Earth’s center a mechanism for generating the geomagnetic field and an energy source for powering it. In 1919, Larmor suggested that the Sun’s magnetic field might be sustained by a mechanism similar to a self-exciting dynamo [3]. Elsasser [4-6] and Bullard [7] first adapted the solar dynamo concept to explain the Earth’s magnetic field being generated by a dynamo-like action in the Earth’s fluid core. The dynamo mechanism is essentially a magnetic amplifier. Since 1939, the geomagnetic field has been believed to originate by convective motions in the Earth’s fluid, electrically-conducting core. The idea is that the convective fluid interacts with the Coriolis forces produced by planetary rotation and acts like a dynamo which is a magnetic amplifier [8]. The idea seemed so logical and seemed to make such sense in explaining the origin of the observed geomagnetic field that for decades no one seriously questioned whether long-term, sustained convection could in fact really occur in Earth’s fluid core. Then along came J. Marvin Herndon who, not only questioned it, but discovered two reasons that convection is physically impossible in the Earth's fluid core [9-11]. Too often scientists toss about the term convection without stopping to think what it actually means and entails. Nobel Laureate Subramanyan Chandrasekhar, pictured at right, defined convection in the following way [12]: “The simplest example of thermally induced convection arises when a horizontal layer of fluid is heated from below and an adverse temperature gradient is maintained. The adjective ‘adverse’ is used to qualify the prevailing temperature gradient, since, on account of thermal expansion, the fluid at the bottom becomes lighter than the fluid at the top; and this is a top-heavy arrangement which is potentially unstable. Under these circumstances the fluid will try to redistribute itself to redress this weakness in its arrangement. This is how thermal convection originates: It represents the efforts of the fluid to restore to itself some degree of stability.” From studies of rock-magnetism, it is known that the geomagnetic field has existed for at least 3.5 billion years. Except for reversals of polarity, the geomagnetic field has been remarkably stable for long periods of time. In fact, at times the geomagnetic field persisted for at least forty million years without reversals. So, if the geomagnetic field is produced by a dynamo mechanism, then long-term, stable convection must necessarily prevail in the operant fluid of the dynamo. But, can stable convection exist for extended periods of time within Earth’s fluid core? This is the question J. Marvin Herndon, pictured at left, addressed [9-11]. For stable convection to exist for extended periods of time in the Earth’s fluid core, it is necessary that an adverse temperature gradient be maintained for extended periods of time so that heat produced beneath the fluid core will cause the fluid at the bottom of the core to be lighter, more buoyant, making it rise to the top of the core, bringing the heat with it. To maintain that “adverse temperature gradient” for extended periods of time requires the temperature at the top of the fluid core to be maintained at a lower temperature than at the bottom of the fluid core. The top of the fluid core can only remain cooler than the bottom of the core if the heat brought to top by convection and by thermal conduction can be efficiently removed. And, therein lays one problem. The Earth’s fluid core is wrapped in an insulating blanket, a rock shell, the mantle, that is 2900 km thick, and which has a considerably lower heat capacity and lower thermal conductivity than the fluid core. Thus heat brought to the top of the core cannot be efficiently removed by thermal conduction. In other words, in the fluid core, an adverse temperature gradient cannot be maintained for extended periods of time, and thus convection cannot be sustained for extended periods of time [9-10]. But, as Herndon discovered, there is another, even more serious, reason that convection is physically impossible in the Earth's fluid core. Because of the over-burden weight, the Earth’s core is about 23% more dense at the bottom than at the top. The tiny, tiny amount of thermal expansion at the bottom cannot make the Earth’s core top-heavy and cannot cause a thermally-expanded “parcel” from the bottom to float to the top of the core as required for convection. Thus, the Earth’s core cannot engage in convection [11]. So, the implication is quite clear: Either the geomagnetic field is generated by a process other than the convection-driven dynamo-mechanism, or there exists another fluid region within the deep-interior of Earth which can sustain convection for extended periods of time. The latter appears to be the case. In 1993, J. Marvin Herndon published the first of a series of scientific articles revealing the background, feasibility and evidence of a nuclear fission reactor, called the georeactor, at the center of the Earth as the energy source for the geomagnetic field [9-11,13-20], which, as Rao notes with extensive references [21], may offer the solution to the riddles of geomagnetic field variability and deep-Earth helium production. The calculations underlying Herndon’s georeactor concept have been verified [22] and extensive numerical simulations have been conducted at Oak Ridge National Laboratory [17, 18] and using computer software licensed there from [19, 20]. In 1996, in a scientific article published in the Proceedings of the National Academy of Sciences USA, Herndon described the georeactor as consisting of a uranium sub-core surrounded by a sub-shell consisting of fission products and products of radioactive decay which may be “a slurry or a fluid” as illustrated at right [15]. In 2007, Herndon presented evidence to support his idea of the georeactor sub-shell being a slurry or fluid, and suggested that the Earth’s magnetic field is produced by a dynamo-mechanism operating in the georeactor sub-shell [9]. Significantly, within the georeactor sub-shell there is no impediment to long-term, sustained convection; heat generated by nuclear fission in the sub-core causes the fluid at the bottom of the sub-shell to be lighter, more buoyant, making it rise to the top of the sub-shell, where it contacts the relatively good thermal conductor heat-sink that is the inner core, which is in contact with another relatively good thermal conductor heat-sink, Earth’s fluid core. Thus, there is no impediment to long-term, sustained convection in the georeactor sub-shell [9-11]. It is expected that convective motions within the electrically conducting fluid (or slurry) sub-shell will interact with the Coriolis forces produced by planetary rotation and act like a dynamo, a magnetic amplifier, as illustrated at right. And, unlike in Earth’s fluid core, the georeactor sub-shell contains large amounts of neutron-rich radioactive fission-produced elements which beta decay yielding electrons for generating magnetic seed-fields for amplification. The georeactor unit thus acts as both the energy source and the operant fluid for generating the Earth’s magnetic field by dynamo action. Even though variations in nuclear fuel occur over time, Herndon's georeactor uniquely is expected to be self-regulating through establishing a balance between heat-production and actinide settling-out [11]. In the micro-gravity environment at the center of Earth, georeactor hear production that is too energetic would be expected to cause actinide sub-core disassembly, mixing actinide elements with neutron-absorbers of the sub-shell, quenching the nuclear fission chain reaction. But as the denser actinide elements begin to settle-out of the mix, the chain reaction would re-start, ultimately establishing a balance, an equilibrium between heat-production and actinide settling-out, a self-regulating mechanism. Because of the self-regulation mechanism, the periods of long-term stable magnetic field production lasting 40+ million years, the so-called "superchrons", are expected. But, what then causes magnetic reversals? The Earth's magnetic field has been decreasing in intensity over the past hundred years. Moreover, as shown in the figure at left, the North Magnetic Pole has recently moved at a rapid rate toward Siberia. These observations are taken by some as a possible indication of a forth-coming magnetic reversal, potentially the first in some 700,000 years.



External influences, Herndon suggests, intermittently disrupt the stability of georeactor geomagnetic field generation and possibly lead to a magnetic reversal. For example, electrical currents induced by superintense solar outbursts could cause heating in the georeactor sub-shell, possibly disrupting convection. Severe Earth trauma might also disrupt convection in the georeactor's sub-shell. Because the georeactor mass is about one ten-millionth that of the fluid core, such changes might occur far more quickly than previously assumed. As described by Herndon [11], georeactor sub-shell dimensions, mass, and inertia are orders of magnitude less than those of the Earth’s core, meaning that changes in the geomagnetic field, including reversals and excursions, can take place on much shorter time-scales than previously thought. External effects that potentially de-stabilize convection in the georeactor sub-shell assume greater importance and pose the possibility of reversals occurring on a time scale measured in months or years. Currently active internally generated magnetic fields have been detected in six planets (Mercury, Earth, Jupiter, Saturn, Uranus, and Neptune) and in one satellite (Jupiter’s moon Ganymede). Magnetized surface areas of Mars and the Moon indicate the former existence of internally generated magnetic fields in those bodies. J. Marvin Herndon has presented evidence attesting to the commonality of matter in the Solar System, which is like that of the deep-interior of Earth, and has made the suggestion [19, 22] that planetary magnetic fields generally arise from the same georeactor-type mechanism which Herndon [9-11] has suggested generates and powers the Earth’s magnetic field. YouTube Video: Origin of Earth's Magnetic Field (click here) This video is best "watched in high quality" as it contains an experimental demonstration of why long-term convection, and hence dynamo-action, in the fluid core is impossible. Return to Home Page NuclearPlanet.com