I have studied astronomy on and off for more than 40 years - including a one-year course on the Solar System with Ian Nicholson at the Hatfield Polytechnic. I have been involved with electricity and electronics for even longer. As a result I have become increasingly dissatisfied with certain aspects of the 'accepted wisdom' promulgated in the books I have read on astronomy. In almost all references to the magnetic fields in the Solar System there seems to be a pre-supposition that they are 'just there' and all movements of ionised gases are affected by the presence of these fields. The references to magnetic fields tend to treat them as the causes of events rather than the reverse.

When I was about seven I was given a book about electricity and magnetism. The book contained a drawing showing a battery, a bulb and a coil of wire in a simple circuit. Near the coil was a compass. I made up the circuit and checked to see if what was written about coils, electricity and magnetism was right. The compass moved when the bulb was lit. It moved back again when the battery was disconnected. From then onwards I have been convinced that electricity always comes before magnetism. It is not a chicken and egg question about which came first. Electricity was first produced in the universe when gases that were hot enough to be ionised began to move, or, when moving gases became hot enough to be ionised. Magnetism was created by the movement of these ionised gases.

Every magnet that ever existed has been created by the primary or secondary effect of an electric current. When a magnet has been made, it can transmit some magnetism to another piece of unmagnetised magnetic material. Unmagnetised magnetic material cannot become magnetised spontaneously. In my studies I have learned about the solar wind and I have read and understood the theory of the Earth's dynamo, based on flows of liquid iron within the Earth. However, this theory does not seem to make much sense to me for several reasons

The main reason is the 'standard' explanation of the circular movement of iron within the Earth. The easiest way to check this is by using a gyroscope as an analogue. The flywheel of a gyroscope is usually made of a conducting metal. How effective would a gyroscope be if it generated a magnetic field as it spun? Gyroscopes do not generate magnetic fields because the atoms and molecules that make up the flywheel are electrically neutral. Any currents generated in one direction are cancelled by currents in the opposite direction. A gyroscope flywheel does not generate a magnetic field, no matter what metal is used to make it or how fast it is rotated.

The iron in the Earth's core must be mobile for the liquid iron dynamo to work. If it is mobile, it must have been stirred and mixed to be in an homogeneous state over geological time. In other words it is likely to be electrically neutral. Neutral rotating conductors generate no electricity, and therefore, no magnetism.

A further reason is the 'standard' explanation of the interaction between the Earth and the solar wind. I have failed to find a satisfying reference to the interaction between the plasma in the solar wind and the Earth's rotation. Let us assume for a moment that the Earth is a sphere in a static fluid. As the sphere rotates, the fluid in contact with the sphere will rotate with it. If the fluid is an electrical conductor, very little will happen because an equal number of moving negatively and positively charged ions will produce mutually cancelling currents. If the fluid is ionised in a particular way, a circular current will form around the sphere.

The solar wind is a plasma that radiates more or less uniformly outwards from the sun, so the circular movement of plasma caused by the Earth's rotation will be displaced towards the Earth on its sunlit side and away from the Earth on its dark side. This effect has been observed by spacecraft. If the Earth was not in a moving plasma field, the current caused by the circular movement of plasma would produce a magnetic field in line with the Earth's axis. As this is not the case, the solar wind speed, the Earth's tilt and the Earth's orbital progress, can account for the offset of the magnetic axis from the axis of rotation. There could be also some relationship between the Earth's precession and the movement of the north magnetic pole?

The distribution of the iron and nickel in the Earth's core may well affect the positions of the magnetic poles. However, when the magnetic fields of the gas planets are considered, comparable differences between spin and magnetic axes are observed. The axis of the Earth's magnetic field is not noticeably affected by the position of the Moon as it orbits the Earth yet the tides clearly show how the Earth is distorted by the Moon's gravity. Because the mass of the Earth's molten metallic core is the major part of the Earth's mass, it must be affected by the moon like the tides, but the effect is hardly noticeable in the positions of the magnetic poles. The Sun's gravity has a lesser effect on the tides than the Moon's. Since the Moon has little effect on the positions of the magnetic poles, the Sun's gravitational effect must be even less. It therefore cannot account for the displacement between the magnetic axis and the rotational axis of the Earth.

I cannot prove that the iron dynamo theory is wrong but I cannot find an electrical analogue to support it. The iron dynamo theory does not seem to fit with the magnetic fields of the gas planets. None of the gas planets contain much iron, and liquid iron is very much less magnetic than the solid element. Dynamo theorists happily substitute hydrogen for iron in the gas planets but, as the gyroscope analogue shows, a spinning magnetic material does not generate a magnetic field. I have not been able to trace a report of research done on the ability of circulating liquid hydrogen to generate a magnetic field.

Jupiter has a high rotational speed and an extensive atmosphere. These factors tend to indicate that the rotational interaction between the atmosphere and the solar wind is largely if not wholly responsible for the magnetic field.

The internal dynamo theory starts to become untenable when one looks at the magnetic field of Uranus. Its axis of rotation is tilted at 98degrees with respect to its orbital plane and its magnetic axis is tilted at 58 degrees with respect to its rotational axis. The orbits of the moons of Uranus and its ring are in line with its equator. Any influence that they might have on the magnetic field would be to make it align with the spin axis. Because the magnetic axis is so far out of line with the spin axis, it must be concluded that the magnetic field is largely if not wholly produced by the interaction of the outer atmosphere and the solar wind.

The magnetic fields of the other planets are observed to be roughly in proportion to their equatorial rotational speeds and the densities of their atmospheres. The internal convective conductive fluid dynamo theory seems to have no relationship with the sizes, densities, compositions and tilts of the various planets and their magnetic fields.

The movements of an ordinary fluid are fairly chaotic, but if the fluid is ionised, its movement is constrained by the magnetic field that it produces. In electronics it is routine to produce and control ionised fluids with high precision. Evidence for this is can be seen on the screen of any television set or computer monitor. Cathode ray tubes in televisions and monitors make use of magnetic fields to control and deflect electron beams. An electron beam creates its own magnetic field that interacts with the magnetic fields produced by the coils around the tube.

A wire carrying an electric current produces a circular magnetic field around itself. The field strength is proportional to the current. An electron beam has similar properties but its magnetic field also increases with speed. Electrons typically travel in wires at around 6.5kph although their effect travels at around 90% of the speed of light in vacuum.

(Compare electrons in a wire with water in a long pipe that is already filled with water. Put in a litre of water in one end of the pipe and almost immediately a litre comes out of the other end - but it is not the same litre.)

Electrons in a beam produce an average cylindrical magnetic field that interacts with the magnetic fields of the individual electrons. An electron with a path that is divergent with respect to average path is constrained by the average magnetic field. The average magnetic field acts like a sort of pipe that keeps the electron within its walls. The strength of the average magnetic field is proportional to the current and the speed of the electron beam. The constrictive effect of the average magnetic field on individual electrons increases as the strength of the magnetic field increases. The result is that an electron beam tends to become narrower as it goes faster.

Electric currents in other plasmas create similar magnetic fields and behave in a similar manner. Lightning and decorative displays that produce lightning effects inside a tube or sphere show this to be true. The illuminated tracks are always very narrow.

An electron beam is one type of plasma. The solar wind is a plasma that is largely made up of protons that are physically much heavier than electrons and carry a similar but opposite electrical charge. The current carried by protons also increases with speed and the constriction produced by the magnetic field they generate increases proportionately. The average solar wind speed is around 600km/s but it can rise to around 2000 km/s or more during solar flares. The particles in the solar wind mix with and are rotated by the earth's outer atmosphere, generating a ring current around the Earth. This creates a bar magnet type of magnetic field which is roughly in line with the axis of rotation of the Earth. The magnetic field assists in the deflection of protons in the direction of the Earth's rotation. In the same way as an electron beam's magnetic field constricts the paths of the individual electrons in the beam, the magnetic field caused by the ring current constricts the paths of the protons that create the ring current in the first place.

Countless millions of separate proton streams form the wind that strikes the Earth's outer atmosphere. The magnetic fields of these proton streams oppose the ring field on the dawn side and are repelled but are attracted to and add to the ring field near the sunset terminator. Electric currents and magnetic fields are always at right angles to each other. Moving ionised particles cannot cross magnetic fields and never move parallel to them. In consequence the field around the Earth acts as a radiation shield against charged particles on the sunward side.

When solar flares occur, the intensity and speed of the solar wind increases dramatically. Approximately 21.5 hours after a solar flare has occurred, the increase in speed and intensity arrives at the Earth's orbit. A very rapid increase in the ring current occurs with a corresponding increase in magnetic field strength. At the north magnetic pole between northern Canada and Greenland, the magnetic field is nearly vertical with respect to the Earth's surface. A large and rapid change in the field will induce currents in conductors at right angles to the field. The most affected conductors are the power lines of the Canadian electricity grid which are parallel to the Earth's surface. The power surges in the grid can cause problems ranging from temporary shutdowns to severe damage to the transformers and switchgear.

If the circulating iron theory for the Earth's magnetic field was correct, the effects of solar flares would be less than they are. The theory implies that most of the Earth's magnetism is derived from circulating iron and not the solar wind. Changes in the strength of the solar wind should thus have only a marginal effect on the Earth's magnetism. The evidence indicates that changes in the strength of the solar wind have a large effect. One must therefore presume that the circulating iron theory cannot account for more than a small proportion of the Earth's magnetism.

The parts of the Earth that are least protected from ionising particles are around the magnetic poles where the higher strength field is nearer the Earth's surface. The ionised particles can penetrate to a lower altitude and excite the gases in the upper atmosphere so that they glow visibly creating the aurorae. The aurorae are bigger and brighter just after a solar flare has occurred.

Geologists have found that the earth's magnetic field has reversed from time to time during the geological past. The circulating iron theory requires a mechanical contrivance to reverse its direction. Geologists have detected nothing that would indicate that the Earth has changed its direction of rotation at any time in the past. One must therefore presume that a very strange and generally harmless process has caused the circulating iron to change direction. What physical law could account for such behaviour? Newton's laws of motion apply. What force could re-route the incredibly massive iron circulation within the Earth without affecting the Earth's surface? Such a force has not yet been conceived even in science fiction as far as I know. A force field that did not affect a planet's surface but could apply billions of tons of pressure 1000 km below a planet's surface would be regarded as silly by most science fiction readers

At present the solar wind consists of predominantly positively charged particles. Protons have sufficient mass to be able to travel continually outwards from the sun once they have achieved the speed of escape from the sun. Isolated electrons have a similar but negative charge and virtually no mass. Electrons quickly change direction when they encounter magnetic fields so they are generally unable to travel far from the sun on their own as protons can do. However, even a body as large as the sun cannot lose protons indefinitely. Sooner or later the sun will build up an extremely large negative charge because of proton depletion. This will attenuate and eventually stop the emission of protons. What happens next would normally be unpredictable. However, the geological evidence indicates that the Earth's magnetic field reverses from time to time, taking about 5000 years to do so. This could mean that the sun starts to emit negatively charged particles, (atoms with extra electrons attached) creating a negative solar wind. If the rotation of the Earth's atmosphere interacting with the solar wind is responsible for the Earth's magnetic field, the magnetic field polarity will change as the solar wind polarity changes. From the Earth's point of view, such a change in the electrical polarity of the solar wind would have relatively few harmful effects. The fading out of a positive solar wind and a subsequent replacement by a negative solar wind would leave the Earth without a magnetic field for a time. The author is not aware of any reports of extinctions associated with changes in the Earth's magnetic field that are comparable to those at the Cretaceous/Tertiary boundary. The change from a positive to a negative solar wind and back again is based on the laws of electrostatics. There are no laws governing a repeated change of direction in an iron dynamo.

If the Earth is excluded from consideration, the magnetic fields of the Solar System planets seem to correspond with two factors - the amount of atmosphere and the equatorial rotational speed. If either rotation or atmosphere are absent, there is no magnetic field. If the equatorial speed is high and atmosphere is plentiful, there is an enormous magnetic field. Jupiter, Saturn, Uranus and Neptune have little iron or any other magnetic elements to create a magnetic field with, yet they all have strong magnetic fields. The dynamo theory substitutes hydrogen for iron in these planets but offers no satisfactory explanation for the differences between their axes of rotation and magnetic fields.

The amount of atmosphere a planet has is related to the escape velocity. Other factors also have an effect. These include the surface temperature and the molecular weight of the gases concerned. The effective angle of incidence of the solar wind on a planet is a function of three speeds and the tilt of a planet's rotational axis. The first is the outward speed of the solar wind. The second is the orbital speed of the planet. The third is the rotational speed around the planet's equator. Perhaps some mathematician could derive an equation which would give the angle of the magnetic axis of a planet from these factors and compare the result with the observed figure.

An alternative method would be to construct a sort of Orrery that reproduces the orbit, rotation and tilt of each of the planets in turn. The axis of the Orrery is set in the middle of a circular pond filled with salt water. An electrode representing the sun is placed under water at the centre of the pond and an annular sheet electrode is placed under water around the periphery of the pond. A rough-surfaced, non-conducting ball, controlled by the orrery, and held under water, represents the planet. The orrery is then set in motion and a check for the presence of a magnetic field around the ball is made. It is unlikely that a magnetic field would be detected under these conditions. The pond electrodes are now connected to a battery and the experiment is repeated. A magnetic field will be detected around the ball. If the experiment is conducted on a large enough scale, it should be possible to determine the axis of the magnetic field of the simulated planet. If the results of this experiment are similar to the observed statuses of the real planets, it must be concluded that the solar wind is the major factor in the creation of a planet's magnetic field.

A related experiment requires a large, non-conducting ball filled with a mixture of salt water and laser toner. [Most laser toners consist of iron dust, carbon black and a plastic binder. The ideal toner for this experiment should remain in neutral suspension in the salt water.] A spherical heater is placed at the centre of the ball. Cooling fans are arranged around the ball. The ball is rotated and observations are made to see if a magnetic field is generated. In this experiment the salt water provides the electrical conductivity and the iron dust provides the magnetic element required for the iron dynamo theory. The heating, cooling and rotational speed should be adjusted to produce a detectable magnetic field. If the heater starts to boil the water before any magnetism is detected, the iron dynamo theory will have received a severe setback.

The following table shows a possible relationship between an estimated magnetic field strength and known planetary factors. The calculations are based on two factors. The presumed magnetism for each planet is based on the escape velocity divided by the speed of rotation The figures for Magnetism ? have been normalised to give a figure of 1 for the Earth. Decimal points have been aligned with the addition of zeros to make figures from different sources consistent. The assumptions have been based on the fact that the amount of atmosphere a planet has is related to its escape velocity. The current generated by the outer atmosphere is in proportion to the speed at which the planet rotates. The magnetism generated is the result of that current. The figures for observed magnetism in the bottom line are taken from a table in Astronomy Today.1

The observed figures quoted for Saturn, Uranus and Neptune are presumably based on Voyager data. This rough and ready way of deriving a figure for the magnetism of each planet seems to have some relationship to the observed data. A different formula for the calculation of the relative amount of affected atmosphere might well bring the estimated magnetism closer to the observed figures. The apparently anomalous figure for Saturn may be due to the properties of its large ring system. The rings may shield Saturn somewhat from the solar wind and thus reduce the ionisation in its outer atmosphere. The other planets' rings are very tenuous in comparison to those of Saturn. Jupiter's figure may be influenced by its inner moons. A plasma torus exists along Io's orbit. This may add to or subtract from the calculated figure in the table. The high estimated figure for Mars may be due to the atmosphere being very much less dense than the escape velocity figure indicates. Mars apparently had liquid water once but there is none now. The same applies to the atmosphere - there is hardly any left. Another factor in addition to the escape velocity must account for the observed lack of atmosphere and consequently the observed lack of magnetism.

The suppositions and calculations made in this document have been based on observed data where possible. The author has not yet been able to find comparable data that would support the "iron dynamo" theory of planetary magnetism. The astronomers questioned on the subject have generally taken the iron dynamo theory as read. However, none has so far been able to offer any explanation that would support the theory except the fact that most planets have magnetic fields.

The electronics literature treats magnetism as an effect produced by an electric current. A magnetic field that has been thus produced can be used to create permanent magnets in a range of iron, nickel and cobalt alloys. However, planetary magnetic fields are not permanent, and, in the case of the Earth, the iron in question is hotter than its Curie point. (The Curie point is the temperature at which magnetic effects in ferromagnetic materials disappear.) The interaction between a rotating planet's atmosphere and the solar wind produces a ring current around the planet. The ring current produces a magnetic field. This fact is not in dispute. The question is: are the ring currents thus produced strong enough to account for the magnetic fields that have been observed? The table of calculations and the manner in which they were derived tends to support the proposition that ring currents account for almost all the planetary magnetic fields observed so far.

A Summary

The possibility that the charge polarity of the solar wind reverses from time to time seems much more likely than a periodic reconfiguration of an iron dynamo. The geologic record includes a very large number of magnetic field reversals that are not apparently accompanied by catastrophic effects. If the iron dynamo was largely responsible for the Earth's magnetic field, the Earth would have had no magnetic protection from an ionised solar wind during the changeover period. Attempts are being made to discover if minor changes to life on Earth occurred during the absences of a terrestrial magnetic field. No records of major changes have been found so far. The Earth would need far less protection from the electrically neutral solar wind that would occur as the solar wind changed polarity. The iron dynamo theory does not offer any explanation of what would happen on Earth if the magnetic field was absent and the solar wind was still electrically polarised.

Final Notes

There are many references to the breaking and linking of magnetic lines of force in books on astronomy. Magnetic lines of force are an imaginary concept used to explain how magnets work. Magnetic field strengths can be defined in contour-like lines that are always closed loops. An open contour line has no meaning. A broken magnetic line of force is equally meaningless. Explanations based on the breaking and linking of magnetic lines of force are frequently found in articles that presume that a magnetic field exists in its own right without any reference to an electric current.

There are also many references to charged particles moving along magnetic lines of force. How easy is it for a physical entity to proceed along an imaginary concept?

A moving charged particle is an electric current that creates a cylindrical magnetic field around itself. The magnetic field is always at right angles to the path of the current. In the case of a current carrying particle that encounters a strong magnetic field, the particle's path is deflected until its own magnetic field aligns with the other magnetic field. Television sets and electric motors rely on this basic principle. A stream of charged particles may be so energetic that its magnetic field is much stronger than the other magnetic field. When this happens, the other magnetic field is distorted to align with the stream's magnetic field. When the magnetic fields are of comparable strengths, the resultant field is shaped in accordance with the proportions of the strengths of the two fields.

An experiment to see the effect of the interaction between a plasma current and a magnet can be carried out with a monochrome TV set or monochrome computer monitor and a bar magnet.

It is best to have a stationary image on the screen to see the effects. One pole of the bar magnet is moved towards the centre of the screen. The image will rotate in proportion to the strength and proximity of the bar magnet. If the experiment is repeated with the other pole of the bar magnet, the image rotates in the opposite direction. The north-seeking pole of the magnet causes a clockwise rotation of the image.

This experiment will demonstrate that the electrons in the beam will align their magnetic fields with the bar magnet's magnetic field. In so doing, their paths are altered to suit. This experiment also shows that the predominant current around the Earth must be produced by protons if the current is responsible for the Earth's magnetic field. The Earth's North Magnetic Pole has the polarity of what would a south pole of a bar magnet because it attracts the north poles of bar magnets. Because the north-seeking pole of a bar magnet rotates an electron beam clockwise, and the Earth's rotation is effectively clockwise as seen from the South Pole, the circulating current that produces a south-seeking magnetic pole at the North Pole must be positive and composed of protons.

A colour TV or monitor screen has a perforated steel plate behind it to align the red, green and blue electron beams with the appropriate phosphor dots. If the steel plate becomes magnetised, the colour purity of the screen may be irretrievably ruined. Never put a magnet near to a colour TV or monitor screen.

Reference 1

I have deliberately avoided using a lot of references because it would be hard to keep the list short enough to be useful and meaningful. Summaries of the present state of received wisdom concerning the solar wind and the Earth's magnetism can be found in Astronomy Today 3rd Edition by Chaisson and McMillan published by Prentice Hall, New Jersey, USA. Copyright date 1999. ISBN 0-13-080100-3.

Other background information has been gained from the Encyclopedia Britannica

Additional notes.

The behaviour of electrons in a cathode ray tube (CRT) can demonstrate that many alleged behaviours of ionised gases as described in books on astronomy are just plain wrong.

The electron beam in a CRT is projected towards the viewer. En route to the screen it is deflected sideways and up and down. A television tube uses magnetic fields to deflect the electron beam. The magnetic field that deflects the beam sideways is created by a pair of coils above and below the neck of the CRT. The sideways deflection creates the lines that make up the picture. A further pair of coils mounted on either side of the neck of the CRT provides the vertical deflection necessary to create what is known as a raster of lines.

From this it can be seen that a vertical magnetic field deflects electrons sideways and a horizontal magnetic field deflects electrons vertically. At no time do the electrons move along "magnetic lines of force" as claimed in many astronomical sources. One must not forget that magnetic lines of force are an imaginary concept. What applies to electrons applies equally to streams of positively ionised gases. Positively ionised gases move in the opposite direction to electrons but the rule is the same: a vertical field causes lateral deflection.

The behaviour of electrons and protons is different because protons are much more massive than electrons. A magnetic field that can deflect an electron stream through 70 or 80 degrees can only deflect a comparable proton stream through less than one degree. Since the space between the sun and Earth is filled with magnetic fields, an electron emitted from the sun is not likely to get very far but a proton could well travel all the way to Earth almost unhindered. An atom that is negatively charged will be deflected in inverse proportion to its mass.

Since the sun is currently emitting protons towards the Earth, the Earth must be gradually accumulating a positive charge with respect to the sun. At the same time the sun must be gradually accumulating a negative charge. At some point the negative charge on the sun will restrict the emission of protons and the positive charge on the Earth will attract negatively charged particles.

wilf.james@ntlworld.com