Source of the Earth's Magnetic Field - mir

For the past several decades, scientists have been struggling with trying to explain seemingly odd aspects of the Earth's magnetic field. Careful measurements have established quite a number of unusual features, like short-term and long-term variations and multiple poles, that have eluded adequate explanation. This article proposes a comprehensive theory that logically explains ALL the peculiar findings, as well as a mathematically and physically logical description of the source itself.

The Problem Symptoms

Rather than having just a fixed North Pole and South Pole, measurements clearly show that there are a NUMBER of additional weaker magnetic poles that exist (that represent about 10% of the field strength!)¹. In addition, the exact location of the North Magnetic Pole on the surface of the Earth continuously changes. Seemingly random movements on the scale of inches or feet occur almost daily, and sometimes in a matter of seconds!² In addition, the North Magnetic Pole seems to also have had a generally westward drift over a period of centuries (of about 1 meter per hour)³.

The complexity gets worse! Not only do the Magnetic Poles seem to wiggle around and drift westward, but they sometimes "jerk" (such as in 1969)² with the motion briefly rapidly accelerating then. In addition to this, the STRENGTH of the measured magnetic field also has a number of variations and drifts. In recent history, the overall strength has been reducing, implying that 1200 years from now, the Earth's Magnetic Field will be zero!⁴

Geologic evidence clearly indicates that the Earth's Magnetic Field has even reversed itself quite a number of times, even within just the past four million years.⁵ ⁶ ⁷ ⁸ ⁹. There is evidence of around 170 reversals during the past hundred million years!

The great age of the Earth, and the fact that there are certainly great frictional forces between various interior portions that are (according to popular theories) supposedly moving relative to each other, would seem to suggest that the Earth's Magnetic Field should have its Poles very near the Geographic Poles, at ninety degrees latitude, if those theories were even remotely true. That is not the actual case, and the Magnetic Poles are located many hundreds of miles from the Geographic Poles. Even more peculiar is the fact that, if you connected the North and South Magnetic Poles with an imaginary straight line, that line would not pass ANYWHERE NEAR the actual center of the Earth! The Earth's Magnetic Field system is not even symmetric with the body of the Earth!¹⁰ Worse yet, the various movements of the location of the two Magnetic Poles often seem to have no relationship with each other.

Previous Explanations

There is strong evidence that there is a significant amount of Iron in and near the Core of the Earth. Due to heat from the environment there, and friction from relative movements of material, some of this Iron certainly becomes ionized, which means charged electrically. This seems quite acceptable as theory.

Previous theorists have assumed that the entire Core (or the Inner and/or Outer Core) rotates as a single flowing object within the Earth. If that were the case, then all of the charged (ionized) Iron material would follow relatively circular paths around a single axis that we could call the Magnetic Axis. Basic Physics tells us that when electrical charges follow a (relatively) circular path (which is effectively a current), a magnetic field is always created as a result. The measured evidence of this scenario would be a simple "dipole" magnetic field, with a single North Pole and a single South Pole, geographically exactly opposite each other on the surface of the Earth.

This is STILL the prevailing theory, (called the "Dynamo Theory") popular today. Some of the basics of it must certainly be true, such as the presence of Iron, its becoming ionized in various ways, its somewhat fluidic flow, and the consequent effect of a general magnetic field from the motion of these charges. However, the Dynamo Theory is unacceptable as it is normally presented, for a number of reasons.

Internal Frictional Drag

Over the Earth's 4.65 billion years of existence, simple Physics shows that friction at the outer surface of that separately rotating (tilted) internal entity would have aligned the Magnetic and Geographic Poles long ago. In addition, that same friction would have continuously reduced the differential velocities at that boundary surface, which would now have to be effectively zero. This would therefore mean that the only remaining rotation that could induce a magnetic field today would be due to the daily rotation of the Earth. That's not necessarily an impossible situation. However, in such case, the locations of the Magnetic Poles would necessarily be virtually identical with the Geographic Poles. Massive evidence shows this not to be true.

Asymmetric Location of the Iron Core

Another complication of this basic Dynamo Theory is that the whole rotating Core would have to be considerably off-center in the Earth, to explain the offset of the line joining the two surface Magnetic Poles. The rotating Iron Core would necessarily have its rotational axis on the line connecting the North and South Magnetic Poles. This would mean that the massive (dense) Iron Core would have to be centered several hundred miles away from the actual center of the Earth. Dynamical analysis of such a situation quickly shows it to be impossible, because such an offset massive Core would cause continuous violent oscillation of the entire Earth! It would also be a dynamically unstable situation that would have centered itself billions of years ago.

Conservation of Momentum

The prevailing theory also necessarily implies a huge amount of rotational inertia for that massive rotating core. This makes the comments of some scientists ludicrous, who explain the observed geologic magnetic field reversals by the reversals of the rotation of the core. No known mechanism could possibly cause such enormous (and violent!) changes of angular momentum, and the effects could not occur in practical time intervals.⁷ ⁸ Other secondary consequences of such a mechanical change must also occur, and evidence of them is non-existent.

Even the most basic mathematical analysis of the rotational inertia and angular momentum of the Earth shows how impossibly large that necessary forces or torques would have to be to cause such physical reversals of the rotation of the Core. And, even if these forces and torques actually could exist, a necessary result of reversing the Core's rotation direction would require (by Conservation of angular momentum) the FASTER rotation of the remainder of the Earth, creating even greater frictional drag between the two counter-rotating portions.

Short-Term Anomalies

This same problem applies equally to explaining the short-term variations in both magnetic field strength and direction and in explaining erratic magnetic pole migration. The phenomenal amount of rotating mass could not change axis direction orientation or rotational rate rapidly enough to cause the measured results, and the force necessary to cause such changes would be beyond imagination. Simple dynamical force analysis shows that. There is no viable source for such a force either. A basic law of Physics has to do with Conservation of Angular Momentum. Even IF some huge torque could come to exist to quickly, incrementally change the rotation of the whole Core over a period of seconds, minutes, hours or days, an equal and opposite torque would have to affect the remainder of the Earth, including the Crust that we live on. Such rather violent movements would easily be sensed. It's just not even remotely possible!

The regular erratic migration of the Magnetic Poles would require a different sort of an internal torque to be applied, to tilt the axis. Simple mathematics shows that even the minor daily movements of the Magnetic Pole Migration would require enormous torques to be applied to tilt the entire Core. In addition to the opposite reaction that would necessarily affect the outer part of the Earth (as mentioned above) an additional effect of torque would appear. That rotating Iron Core would be essentially a giant gyroscope. If a torque was quickly applied to alter the the axis of any gyroscope, an acceleration in the third-dimension would appear, a standard fact of Physics. No evidence of this exists.

Mathematical Analysis

The multitude of speculations presented as 'explanations' for the presence of the Earth's magnetic field, do not generally seem to be backed up by any serious dynamical analysis. This is surprising, and the author has searched for such mathematical support by those other sources. If such analysis was done by them, it seems likely that they would see the impossibility of various of their speculations. The following is a very simplistic analysis of the dynamics that would have to exist in the standard Dynamo Theory.

First of all, we think we have a reasonable idea on the physical sizes of the Inner and Outer Core. The current estimates for their radii are 1275 km and 3500 km, respectively. The Outer Core is generally considered to be fluid, and therefore capable of the necessary flow, so we will consider it. The volume of the Outer Core can be simply calculated as about 1.62 * 10²⁶ cm³. With its estimated density of 10 gm/cm³, that indicates a total mass of around 1.62 * 10²⁴ kg. Using Avogadro's number, this indicates approximately 5 * 10⁴⁶ atoms are involved.

It is unknown just what proportion of those atoms are Iron and/or what proportion of them are ionized into being charged. For this discussion's sake, we are going to take a conservative estimate, that one in a million of the atoms are ionized.

As a side comment, virtually all comments on this subject imply that Iron specifically is necessary in the creation of the Core electrical currents. That assumption seems unnecessary, as ANY fluidic material that can be ionized would carry the necessary electrical charges in the relatively circular paths necessary to create the electrical currents.

This now suggests that we would have a total of around 5 * 10⁴⁰ electronic charges flowing in the Outer Core.

There has also been much unsupported speculation as to the flow characteristics of the Iron in the Outer Core. For this discussion, we will momentarily accept the opinion of a well-respected authority that the Iron at the extreme high temperatures of the Core, flows 'like water'. If this is the case, the relative motion of the Iron might easily be on the scale of 'slow walking speed' or 1 meter/sec.

Given the dimensions of the Outer Core, we can determine that this corresponds to one full 'orbit' in around 4 years. This results in around 4.4 * 10³² ions/second passing any point in the circuit. This corresponds to an electrical current of around 7 * 10¹³ Amperes.

The Magnetic Flux created by an electrical current is given by the standard equation: (Flux) = 0.4 * (pi) * N * I / (l / A * (mu)) equation. In this case, N is 1 turn, I is 7 * 10¹³ Amperes, A is around 1.8 * 10¹⁰ cm². The magnetic relative permeability (mu) for Iron at extremely high temperatures and pressures is not accurately known, but it seems to rise with temperature and seems certain to be at least 10,000. (l) will be consider as around 4 * 10⁹ cm. Plugging all these values into the equation gives a result of a Magnetic Flux of around 4 * 10²⁵ Maxwells.

At the surface of the Earth, this would result in a Magnetic Flux Density of around 30,000,000 Gauss!

Seeing that the ACTUAL measured Flux Density is around 1 Gauss, this standard Dynamo Theory seems to give a field millions of times too intense! The uncertainties in the values of the magnetic relative permeability and flow rates/viscosity of the Iron do not seem to adequately deal with such an incorrect result.

Other scientists have offered quite a variety of additional speculations to try to explain one or more of the unusual aspects of the Earth's Magnetic Field. Generally, they seem to try to just "glue on" some extra feature, while often neglecting some basic laws of Physics. Sometimes their added features eliminate any possible simultaneous explanation of other unusual aspects that have been recorded. Therefore, unless a scientist considers the dynamical Physics involved, and does the math to assure conservation of rotational inertia, angular momentum, and all the other basic rules of Physics, his suggestions should be given little credibility. For example, a recent speculation¹¹ that a large meteorite hit the Earth, kicking so much dust into the atmosphere to change the climate, to melt the polar caps, to let more mass of water flow nearer the Equator, to change the relative weight loads in different areas of the Earth, to cause pressure differences thousands of miles deep at the Core-Mantle boundary, is just that, wild speculation. This "theory" was proposed in 1986. The mechanism described does not even remotely stand up to dynamical analysis of the Physics involved, and seems hardly worth mentioning, except for the shallowness of the science being applied.

A Better Dynamo Theory

Instead of the Earth's Core being considered a single contiguous rotating object, it seems to make much more sense to consider it being a number of individually active heat-driven convection cells. These cells DO have the rather rapid fluid flows previously speculated, but they are driven by heat rising from the Inner Core, with its radioactive decaying heat sources. The convection cells are therefore edgeways to the Inner Core, offering an efficient method of removing heat that accumulates in the Inner Core. As the rough calculations above imply, these cells, with their relatively rapid flow rates, EACH create very large electrical currents. However, the circumstances around the Inner Core suggests that a general Symmetry must primarily exist, and similar Outer Core convective cells must generally exist on opposite sides of the Outer Core and rotate in opposite directions. The resultant measured Magnetic Field Strength measured at the surface of the Earth would therefore be the summation of a multitude of these generally opposing magnetic field generators.

So, even though EACH convection cell is creating a Magnetic Flux a hundred or a thousand or more times greater than necessary to explain our measured surface Flux Densities (as calculated above), the great majority of those (dipole) effects cancel out due to the presence of essentially identical counter-rotating convection cells on the opposite sides of the Outer Core. The result is a measured Magnetic Field Strength that can display extreme and erratic fluctuations in both short and long time periods, including regular apparent pole reversals. In addition, this premise includes explanations for the quadrupole and octopole and higher components of the measured field strengths and many other previously unexplained features of the complexities of the empirical measurements.

To present this most clearly, it will be simplest to first consider a situation where there were just two convection cells in the Core. We will later extend the concept to a possible multitude of Core convection cells that probably actually exist.

A Two Convection Cell Model

Consider a situation where there is a heat source at the very center of the Earth, and that it is surrounded by a viscous fluid. Next, realize that such a viscous fluid would soon develop natural convection cell flows to carry heat away from the central heat source. For the moment we are going to assume that there are just two of these convection cells. We will consider them to be symmetrically opposite the central heat source. We are also going to temporarily assume that the flows in the two cells have identical shaped flow paths, flow rates, and all other dimensions.

We will make one other very reasonable assumption. The flow direction of the two cells are such that the material in the flows nearest adjacent to each other in both cells move parallel to each other and not oppositely. Any alternative to that would involve extensive turbulence and a great amount of friction between the two. After a 4.5 billion year existence, it seems reasonable to conclude that a relatively stable relationship would have developed where the two flow paths would now flow smoothly along side each other where the cells were adjacent. With our two-cell model, this requires the two cells to rotate in opposite directions.

We believe that there is a considerable amount of Iron in the Earth's Core. We also know that flow and friction and heat tends to create ions as electrons are dislodged from atoms. The ionized Iron in the viscous material flowing in the two convection cells now represents two enormous electrical currents. Each cell will therefore create a magnetic field of its own. Due to the "right hand rule" of electromagnetic theory, the direction of the magnetic fields thus created by the two cells will be OPPOSITE one another. For a magnetic sensing device at a great distance away, these two exactly equal and exactly opposite magnetic fields will therefore totally cancel out, and there will be NO evidence of any (dipole) magnetic field. (Because of the lateral displacement between the two field sources, there WILL, however, be evidence of a quadrupole magnetic field, if the sensing device can recognize it.)

Let us now say that EACH of the two magnetic fields present are one hundred times as strong as the dynamo strength previously accepted in theories. If either existed alone within the Core, we on the surface would measure a magnetic field one hundred times as great as we now measure. However, since they TOTALLY cancel each other out, still NO dipole magnetic field would be measured (at a sufficient distance).

Now, let's modify one of our previous assumptions. Instead of the two convection cells being precisely identical, they are very slightly different from each other. This could be due to the overall dimensions of the cell, the velocities of the flow rate, the proportion of ionized Iron present in the cell flow, or any of a number of other possible differences. These small differences between the two cells are dynamic and temporary. Over a long time interval, they would average out, implying approximately equal time periods where each of the two were slightly dominant.

The changes we are proposing here are rather subtle, where one of the convective flow electric currents, and therefore the resultant magnetic field is increased by only one per cent in strength. This rather minor change will have a tremendous effect. Now there WILL be a net measured magnetic field at a distance. The magnetic field strength measured will be effectively the DIFFERENCE in the strengths of the two opposing fields, and therefore of a strength just one per cent of the strengths of the two very strong fields actually created by the individual convection cells. With the parameters chosen for this example, that one per cent differential would register on our measuring devices at the Earth's surface as the accepted field strength we now know to exist.

This situation would ALSO create a quadrupole magnetic field. Mathematical derivation of the strength of the resultant quadrupole field is rather involved, and it is dependent on a large number of variables, including the spacing between the centers of the two convection cells.

This model is dynamically viable for the environment believed to exist in the Core of the Earth. All previous theories have been subject to substantial frictional drag slowing down the source materials and therefore reducing and then soon eliminating the magnetic field existant. This theory acknowledges such frictional drag continuously slowing each convection cell, but accepts that the central heat source would then either re-energize those cells or create new and different cells. In any event, SOME cells would HAVE to exist, to enable the heat from the central source to be carried away and outward. Equally important, virtually always, symmetric PAIRS of such convective cells must form and exist, for dynamic stability reasons.

Conservation of mass, momentum, angular momentum, and other basic laws of Physics would imply that a lot of symmetries would be likely to exist in the convection cells created and maintained in the core. The relative similarity of the two cells in our example, and their locations symmetrically opposite each other from the central heat source, can be shown statistically to be generally preferred situations.

Resolution of Several Problems

The fact that this theory suggests that the Earth's Magnetic Field measured at the surface (or in space) is a result of the vector sum of two much stronger but generally opposing source fields, enables straightforward explanation of many of the peculiar characteristics measured in the Earth's Magnetic Field.

Rapid Variations in Measured Magnetic Fields. If either of the two source convection cells has a slight change of heat intake from the central heat source, or if ANY of a large number of parameters slightly changed, the magnetic field produced by that cell could change fairly quickly (in days, hours, minutes) by an amount of one part in ten thousand. Such a tiny change, in a single convection cell which has substantial total size, mass, and rotational momentum and inertia, would represent a full one per cent change in the measured field intensity at the Earth's surface. Since only a moderate variation of amount of ionized Iron being transported in that cell, or localized heat input to that cell, or the cell movement path is involved, such a change COULD occur during a very short period of time.
Complex Nature of Measured Magnetic Fields. Even our simple two-cell model gives both dipole and quadrupole magnetic fields at the surface of the Earth. Once we consider additional Core cell pairs, octopole and higher fields would exist. If these additional Core cell pairs were at skew angles to the first cell pair, very complex surface magnetic field strength patterns would be measured.
Magnetic Reversals. Magnetic reversals would be easily explainable, and even extremely likely, with this model. In the stronger cell of our two, if some parameter changed slightly, that cell could soon (in a few thousand years) produce a magnetic field that is two per cent weaker than before. The result of this, as measured at the surface of the Earth, would be a total reversal of the net magnetic field measured there. Again, a two per cent net change in convective flow in one of the two cells is very realistic over a period of a few thousand years.
Extensive analysis of volcanic rocks at Steens Mountain in Oregon suggests that a reversal took about 4500 years to complete, during the Miocene epoch. During that time, it would appear that the magnetic poles wandered wildly, and even crossed the equator three times! This erratic record of magnetic fields are easily explainable by this approach, while no other theory can even remotely explain it.
Magnetic Drift and Secular Variation of Intensity. Slow variation in each of the two convective cell flows is certain to occur. If the effect is in one getting gradually stronger or weaker, the result would be a measured gradual change in field strength at the Earth's surface. If, instead, the change was in a gradual orientation change of a convection cell, the result could also include an apparent gradual drift at the Earth's surface of both the measured field line angles and the perceived locations of the North and South Magnetic Poles.
A General Preference for the dipole portion of the field measurable at the Earth's surface to be either moderately co-axial or anti-axial with the rotational axis of the Earth itself. I haven't seen anyone else address this matter, but it appears to be generally true that magnetic North has nearly always been approximately actually North or actually South. This theory provides an explanation for this situation. The entire Core generally rotates WITH the rest of the Earth, that is, every 24 hours and around the geographic axis of our planet. This rotation of the Core adds an additional angular momentum to all the viscous materials that compose the Core. Statistically, this establishes a preference for convective flows and symmetries associated with that geographic axis. Therefore, when the measured magnetic field intensity (of a pair of core convection cells that are at a skew angle) reverses at the Earth's surface, it DOES approximately reverse and doesn't just go to a random orientation.
Disparity between the Earth's Magnetic Axis and its Rotational Axis. The comment just above indicates why there is a preference for the magnetic field to be generally parallel or anti-parallel to the rotational axis of the planet. However, the effect of the differential between the two cells is certain to be an effect of greater magnitude. This means that it is briefly possible for the magnetic poles to be in tropical locations during the times of magnetic reversals. Even with just the two convection cells of our simple model (oriented possibly at a skew angle within the Outer Core), an amazing diversity of possible measured magnetic fields at the Earth's surface is possible. Because of the effect of the rotation of the Earth, such anomalies would seem to be of relatively short duration. In other words, it seems that any orientation of the Earth's Magnetic Field is merely meta-stable. Continual dynamic small changes in the Core convective cells will forever keep altering the measured field strength and direction vector, until such day as the Earth cools so much to stop those convective cells.
In 1990, some scientists speculated that the Earth's Magnetic Axis is not actually inclined as it has always been believed to be.¹² They suggested that the magnetic dipole axis was parallel to the Earth's rotational axis, but that there were some unspecified additional dipole moments that are responsible for the apparent tilt of the magnetic axis. It does not appear that they have tried to do computer simulations of their concept. Their idea of a few small dipoles affecting the observed results so greatly seems really doubtful, but there is a vague similarity between their idea and this present theory. This present theory agrees with them in that the Core generally rotates on an axis virtually identical with the Geographic Axis. It must, because of frictional considerations and the great age of the Earth. However, the present theory presents a far more reasonable explanation for the present displacement of and (independent) movements of the observed Magnetic Poles by differences between the shapes or flow rates of the two massive opposite convection Core cells which might happen to presently be oriented at an angle to the axis of the Earth's rotation.
This new theory also explains the peculiar magnetic fields around some of the other planets, notably Uranus. The great disparity between the present magnetic axis and the rotational axis of Uranus (60 degrees) ¹² would be seen as evidence that the planet is in the process of a field reversal, and that it will eventually get to a meta-stable situation of being generally co-axial or anti-axial. It might be extremely valuable to regularly monitor that field, as possible insights into Earth's dynamic structure.
The Earth's Magnetic Axis does not pass through the Center of the Earth. The logic of the previous two subjects above also explains this oddity of the Earth's Magnetic Field. There is also the implication that the apparent movement of the two Magnetic Poles can be almost entirely independent. Even though the Core is actually centered within the Earth's body, the effects of differing opposite (tilted) convective Core cell shapes or flow rates could result in Magnetic Pole positions substantially away from the Geographic Poles. The effect of additional pairs of opposite convective Core cells could enhance this characteristic. Further research might confirm this independence of Magnetic Pole positions.

A Multitude of Convection Cells in the Core

Even our simple two-cell model has made it possible to describe many of the unusual features seen in the Earth's Magnetic Field. Rather than two, there seem likely to be a multitude of such convection cells. Again applying symmetry arguments and the various conservation laws that we know should apply there, there is great statistical support for believing that they often exist in symmetric pairs, that have great similarity to each other, with opposite flow rotation, and where, as before, only the net effect of the difference between the pair gives any evidence of dipole magnetism. This also implies that, not counting eddy effects, there must be an even number of such active large convection cells at any moment. The fact that the Outer Core is three-dimensional, with heat-driven convection cells possible at all locations and with all orientations within it, make for the possibility of extremely complex flow structures. However, the Symmetry arguments still hold, and pairs of opposing cells must certainly be the dominant situation.

Additional aspects of empirical evidence can now be explained:

Earth's Field Complexity. Since the magnetic field measured at the surface (or in space) is the vector sum total of many convective cell generated fields, dipole effects, quadrupole effects, octopole effects, and many other, more complex features are explainable. With the dynamic nature of each originating convective cell, all of these contributions and effects are independently variable, both in intensity and orientation.
Jerks and Glitches. The very short-term changes that have been observed in the Earth's Magnetic Field, could be explained as the creation, disappearance, or change, of small convective eddies in the Core. Most of the centrally generated heat will likely be carried outward by large, relatively stable, convection cells, but turbulence must certainly sometimes occur, which would create short term eddy flows. There is SO little data to work from, it seems speculative to try to determine Reynolds numbers to try to determine whether the flow rates in the convective cells is laminar or turbulent. Maybe, some day, it will be possible to infer such analysis. Until then, it seems likely that at least occasional eddies would occur.
The evidence of the magnetic reversal of 15.6 million years ago, recorded in the lavas of Steens Mountain (mentioned above) suggests that the orientation of the magnetic field sometimes changed as rapidly at 3-8 degrees PER DAY during that episode! A brief but intense Core convection eddy could easily explain this amazing finding. This theory actually allows several similar explanations for such findings. Previous theories cannot even speculate on an explanation for it.
Core-spot pairs. Recent research, especially from space magnetometers, has found evidence that localized dipole pairs seem to exist and to move around, especially in and near the Indian Ocean. ¹ These measurements may just be artifacts of the continuously varying vector sum total of several large constituent magnetic fields and some brief eddy current fields.

Conclusion

Evidence keeps accumulating regarding the great complexity of the phenomenon of the Earth's Magnetic Field. Historic evidence from the past two thousand years shows extensive variation, both in strength and orientation, and also great differences between effects and changes at different locations on the globe. Mid-Ocean ridge Magnetic Banding suggests numerous total reversals of the Earth's effective magnetic field in the recent few million years. The empirical field strengths and orientations and the anomalies and drift of the Earth's Magnetic Field are extremely complex. Competing theories cannot explain the diversity of unexpected findings. This present approach is easily capable of explaining all the curious aspects of the phenomenon of the Earth's Magnetic Field.

None of this requires any new forces, torques, laws or mechanisms. Even when very rapid and abrupt changes would be happening to the magnetic field, very little mechanical stress is present in any part of the structure of the Earth. No effect of any of this would shake or vibrate or be otherwise destructive to our planet.

Future

It might be productive if a super-computer was assigned the task of determining a possible combination of N convective cells, each of which could have a wide range of dimensions, shapes, flow rates, orientations, and ionized Iron content rates. Science has accumulated a huge storehouse of magnetic field strengths and orientations, both from the ground and from space, with which such a computer could be fed. In addition, some sort of Fourier analysis might be possible to enable us to recognize individual convection cell contributions in the measured results we have amassed.

It would seem prudent to try to monitor the magnetic field of Uranus, to determine whether the present orientation of its magnetic axis is transitory or meta-stable. We may be observing an ongoing example of a magnetic reversal, knowledge of which should assist us in better understanding the history and dynamics of our planet.

Notes

The Earth's Inner Core is generally described as solid. This is a relative term. For behavior during the passage of shock waves, such as earthquake waves, through it, the viscous materials act as a solid. But, for the immense circulations described here, there can still be slow but significant flow. The result is a very low VOLTAGE flow, but with immensely high CURRENT. That slow circulation is what causes the individual convection Core cell magnetic fields described.

Theoretical ideas about the vertical distribution of elements in the Earth has always been primarily based on the behavior of earthquake S- and P- waves, on the total mass and rotational inertia of the Earth, and on the composition of extra-terrestrial meteorites found on Earth. These empirical results have been combined with the concept of vertical segregation of minerals and elements by weight, to suggest that the heavy elements (including mostly Iron) would have migrated (in an earlier, more molten Earth) toward the center Core and the lighter elements and minerals (including gases) would migrate toward the outer Crust.

The opinion that the Core is two parts, which are solid and liquid, is primarily based on a shadow-effect on earthquake-generated waves. The concept of solid is somewhat a relative term. Very tall mountains are considered solid, even though they have clearly documented very slow flow rates, so, in some sense, those mountains are fluid, and the flow rates have even been measured. Thus, a solid Core can generally be said to be true (as regarding rapid earthquake waves) while still involving relatively slow flow rates. This circumstance would have the effect of acting as solid for the earthquake generated shock waves, but would still allow fluid flow. Such slow flow would cause two additional consequences. First, the very heavy elements could migrate even more centrally, to the Inner Core, including the primary sources of long-term natural radioactivity (such as Uranium). This new perspective would put the Earth's primary inner heat source farther toward the middle of the Earth. Second, this situation would certainly represent an energy source which would drive the proposed (rather slow) convective movements in the Core.

This possible Inner Core convection would probably tend to stir up the very heavy elements in the center of the Core, so the vertical (radial) segregation may not be as distinct as it could otherwise be. More importantly, this slow convection would likely create a variety of meta-stable, limited-lifetime randomly oriented convection cells in the Core. These cells would be somewhat dynamic and fluctuating, in various locations and of variable number. Each such cell would effectively generate an electric flow in a circuit, and would thus create a magnetic field. These convectively created magnetic fields would likely have components that were generally NOT co-axial with the rotation of the Earth itself!

The individual magnetic fields created by the individual convective Core cells would not be easily noticed or measurable from our perspective at the surface of the Earth. The net, measurable Core magnetic field would be a vector combination of all of these cell-based magnetic fields. MUCH of the effects of the magnetic fields due to specific Core convective cells would be cancelled out by the magnetic fields created by OTHER Core convective cells with opposite circulation flows. For example, two exactly identical convective cells on opposite sides of the Core, would, (due to the Right-Hand Rule of magnetic field orientation as a result of an electric current) cancel each other out! There would be no net dipole effect of the magnetic fields generated by these two Core convective cells. (There WOULD, however, be a quadrupole magnetic field present, because the two sources were spatially separated from each other) Analysis of quadrupole and octopole components of the measured field strength might be especially productive in learning about the specific cell orientations.

This same result could occur from say, SIX convective cells, IF the resultant magnetic field vectors of the six added to a null vector, AT THAT POINT on the surface of the Earth or in space. Such a total cancellation would not generally be possible over an extended area of the surface of the Earth. Analysis of field strengths at adjacent areas should enable reconstruction of the necessary component source fields in the Core.

The net effect of a multitude of Core convective cells would thus have a VERY complex nature, and would certainly NOT act like a simple magnetic dipole. During short time intervals (like decades), this net Core magnetic field would create a measurable Earth magnetic field that seems stable and relatively constant. Small, continuous variations of field intensity and effective magnetic pole location would be expected, as are observed. The current premise would also explain the quadrupole, octopole (and higher) components empirically measured in the Earth's magnetic field.

Of course, many other opposite pairs and generally randomly oriented convective eddy cells could exist at various other angles around the circumference of the Core. Keep in mind that this situation is true in three dimensions, so that there are likely to be convective cells completely surrounding the center of the Core. The net magnetic field of the Earth, as measured at its surface, would be the sum of all these constituent components, making for a measured magnetic field with a LOT of fine detail.

The rotation of the Earth itself would certainly have some effect on the formation and durability of the various constituent Core convective cells. Internal friction should certainly have caused a "general" rotation of the Core that would be moderately co-axial with the rotation of the physical body of the Earth itself. This logic would imply that there would likely be a tendency (but not a necessity) for the axis of the Earth's Magnetic Field to be generally co-axial or anti-axial with the Earth's rotation axis. Further study would be necessary to determine which orientations of Core convective cells would become preferred and which would quickly disappear. This effect might contribute to the empirically identified Reversals of the Earth's magnetic field, rather than just causing random orientation of it. It it would be true that one symmetric pair of convective Core cells predominates, the situation would be similar to that described in the simple Model above.

Over longer time periods, say thousands of years, the effect of stirring up some of the central radioactive materials would cause changes in the locations of some of the Inner Core's heat sources, which would have considerable effects on changing the Outer Core's convective cells flow patterns. Even fairly minor changes in a few of these convective cells might change the NET effect (at the surface of the Earth) so much so as to reverse the Earth's effective magnetic field.

Again, the (net) total field measured at the surface of the Earth is the sum of the magnetic fields of many such pseudo-randomly oriented convection cells (or symmetric cell pairs), so that the total net measured effect could fluctuate erratically and quickly. It is important to note that the magnetic field strength of an individual Core convective cell is FAR larger and more constant than the net effect of an opposing pair. The present premise suggests that this is what allows the rapid, large, erratic fluctuation in the net Earth's magnetic field, both short-term (which we now continuously measure) and long-term (as recorded in magnetic banding in sea floor spreading and in cooled volcanic flows).

This premise also explains the heretofore unexplained quadrupole and octopole magnetic moments of the Earth's magnetic fields, and suggests that thorough analysis of those effects might give some insight into the actual distribution and orientation of the Core's constituent convective cells.

If movement of some of the central radioactive element heat source was such that even one of the Core's convective cells materially changed, the NET magnetic field of the Earth could be significantly and rapidly altered. Even if it wasn't reversed, the Poles might suddenly (over a few hundred years?) jump thousands of miles.

This theory also explains something that no one has seemed concerned about. When the Earth was originally formed, it might have somehow been true that the Core's rotational axis was (briefly) not co-axial with that of the Mantel and Crust. But over the extremely long time the Earth has existed, frictional drag at the Mantel-Core boundary would certainly have caused these axes to have become co-axial long ago. Most competing theories about the source of the Earth's magnetic field have the Core rotating at an angle, such that it is lined up with the present Magnetic Poles. That situation appears to defy the laws of science. The present premise does NOT require this, and includes a mechanism for explaining the separation of the Geographic and Magnetic Poles. This premise allows the much more logical generally co-axial rotation of all the major components of the Earth.

Footnotes

¹Weisburd, Stefi; "The Inner Earth is Coming Out," Science News, 131:222, 1987.
²Whaler, K.A.; "Geomagnetic Impulses and Deep Mantle Conductivity," Nature, 306:117, 1983.
³Kerr, Richard A., "Magnetic 'Jerk' Gaining Wider Acceptance," Science, 225:1135, 1984.
⁴Anonymous NASA; "Magsat Down: Magnetic Field Declining," Science News, 117:407, 1980.
⁵Wei, Q.Y., et.al.; "Intensity of the Geomagnetic Field near Loyang, China, between 500 BC and AD 1900," Nature, 296:728, 1982.
⁶Wei, Q.Y., et.al.; "Geomagnetic Intensity as Evaluated from Ancient Chinese Pottery," Nature, 328:330, 1987.
⁷Appenzeller, Tim; " A Conundrum at Steens Mountain," Science, 255:31, 1992.
⁸Lewin, Roger; "Earth's Field Flips Flipping Fast," New Scientist, p.26, January 25, 1992.
⁹Prevot, Michel, et.al.; "How the Geomagnetic Field Vector Reverses Polarity," Nature, 316;230, 1985.
¹⁰Dziewonski, Adam M. and Woodhouse, John H.; "Global Images of the Earth's Interior," Science, 236:37, 1987.
¹¹Muller, Richard A. and Morris, Donald E.; "Geomagnetic Reversals from Impacts on the Earth," Geophysical Research Letters, 13:1177, 1986.
¹²Akasofu, S.I. and Saito, T.; "Is the Earth's Dipole Actually Inclined with Respect to Its Rotation Axis?" Eos, 71:490, 1990.

First Developed, March 1996,
First Published on the Web: June 22, 1997

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C Johnson, BA Physics, Univ of Chicago