by Bruce Maccabee (c)B. Maccabee, 1994,2000 (This paper was originally presented at the American Physical Society meeting in April, 1993 [Bulletin of the American Physical Society, Vol. 38, pg 1041, 1993] and published in the Journal of Scientific Exploration, Vol. 8, pg. 347, 1994.) ....................................................................... ........................................................................


Perhaps some UFOnauts have magnetic personality. Anyway, one UFO appears to have "left behind" a strong magnetic field. This paper reports the discovery and significance of that field. On Friday, Sept. 11, 1992, at approximately 6:20 PM Mrs. A (name confidential; she holds a high-level position at a bank) was entering the driveway at her home in Gulf Breeze, Florida when she saw to the northeast, over the roof of her house, an unusual round object rise upward, move to the right a short distance while flipping over (see Figure 1) and disappear in the clear sky. _______________________________________________________________________ _______________________________________________________________________ It appeared brownish-grey at the top and bottom with a pinkish-red line around its circumference. The center of the bottom seemed to be glowing. The object was at some distance and apparently had risen upwards from behind her house where there is a lawn, a pond and trees. The total duration of the sighting was several seconds. Within an hour or so the witness told her husband, J, (who also wishes anonymity) about the sighting. Several hours later he contacted two local UFO investigators, Bland Pugh and Bruce Morrison, both members of the Mutual UFO Network. (Note: the MUFON investigators were quite well known in the area of Gulf Breeze and Pensacola, Florida because of the numerous newspaper, radio and TV stories about sightings in the area that started in late 1987 and continued into 1992.) They agreed to visit the site during the afternoon of the next day.


There were thunderstorms in the area and it rained for a while late Friday night. The next morning J used a transit to determine Mrs. A's sighting line direction from her observation point in the driveway. He then decided to search the area behind the house to determine whether or not there was any trace of magnetism left by the UFO. He decided to search for a magnetic field because many years before he had had a UFO sighting which, in his opinion, involved a strong magnetic field. One night in 1973 a bright UFO had passed over his car and afterward the gauges on the dashboard, including the non-electrically operated oil pressure gauge, all pointed roughly toward the steering column, a shaft of magnetizable iron. He believed at the time that a strong magnetic field associated with the UFO had magnetized the steering column causing the needles to point toward it. At that time he had no instrument to confirm that there was a magnetic field. But in 1992 he had a very sensitive device, a flux gradient magnetometer or "gradiometer" (model GA-52, manufactured by the Schoenstedt Instrument Corporation (reference: Schoenstedt), which he has used during the last ten years to search for buried oil well casings (iron pipes) as part of his work.


The gradiometer is a battery powered device which has a cylindrical rod (pipe) called a "wand" that is attached to a cylindrical case (see Figure 2). ________________________________________________________________________ ________________________________________________________________________ In the wand are two rigidly mounted fluxgate magnetometers (Primdahl, 1979) with their axes oriented along the rod and which are spaced about 51 cm apart. Each fluxgate is sensitive to the component of the magnetic field, B, along the axis of the wand. The electronic circuitry in the cylindrical case creates the magnitude of the difference in the component B values sensed by the two fluxgates. (The circuitry does not determine which way the field is pointing along the axis, i.e., it does not distinguish between "forward or backward" along the axis of the gradiometer.) This difference, divided by the spacing, is the magnitude of the gradient of the field along the direction of the wand. Hence the device is called a gradiometer. The electronic circuitry also generates an audio tone that drives a loudspeaker in the cylindrical case. The most important characteristic of the device for purposes of scientific research of magnetic fields is that the frequency, f, of the tone increases monotonically with the magnitude of the gradient. Furthermore, over a reasonably wide range the frequency,f, is roughly proportional to the gradient: f = K times(the magnitude of the difference), where K is the calibration constant. The gradiometer is a rugged field device that was designed for locating magnetic field "sources" such as buried iron objects. (Note: here the term "source" is applied to any object or material which either has its own magnetic field, such as a magnet, or which distorts the earth's field in the vicinity of the object, such as a piece of iron.) A field source could be a magnetized material or a ferrous (permeable) but non-magnetized material. It can detect non-magnetized ferrous materials because they distort the earth's field and the gradiometer detects the field gradient caused by the distortion. For example, a representative of the Schoenstedt company told me that at its most sensitive setting it could detect a piece of iron the size of a manhole cover at a distance of about seven feet. The gradiometer is typically operated in the following manner: the operator holds the wand where it joins the cylindrical case and, while walking over the area to be searched, he "waves" it around, thus moving and rotating axis of the fluxgates. At each location as he moves the operator searches for the location and direction of the wand where the frequency is the highest. When this is found the operator moves a short distance in the direction the wand is pointing and again waves it around to find the highest frequency. If the operator is now closer to the source the new maximum frequency should be higher than the previous maximum frequency. A large buried piece of metal can be found in this way because the wand points generally in the direction of the source of the field gradient, thereby leading the operator toward the metal. However, at many locations the gradient may actually point slightly away from the direction to the source. For example, at most locations in the field of a simple dipole source the maximum gradient points several degrees of arc away from the direction to the center of the dipole. The operator can compensate for this by doing enough of an area search to localize the area where the frequency is the highest. This localized area contains the source of the field. The same mode of operation can be used to locate any source of magnetic field, whether underground or not.


J began his search by following a footpath that leads around the west (left) end of the pond and then eastward on the north side the pond (see Figure 3 which is only approximately to scale). He was continually waving his gradiometer in various directions to the left and right while pointing it toward the ground and also upward. ________________________________________________________________________ _________________________________________________________________________ As he approached the east end of the pond he began to notice an increase in frequency. He subsequently determined that the frequency was highest when he stood on the shore of the pond, approximately at the location of the triangle in Figure 3, and pointed his instrument upward and over the pond. He believed that either he was detecting a "magnetic cloud" in the air over the pond or else his instrument was not operating correctly. He checked the operation of his instrument at a location a considerable distance away from the magnetic field and convinced himself that there was nothing wrong with the gradiometer. He then continued his search around the pond and discovered an area where he obtained the highest frequency when he pointed the wand straight upward or nearly so. This area, which seemed to him to be beneath the source of the field, was under some pine trees on the south side of the pond (see Figure 3), about 60 feet (18 m) from where he first detected the field. His impression was that the source was actually at or above the tops of the trees.


He also noticed, while looking over the 4 to 5 foot deep pond, that there were three circular areas of depressed pond grass at the bottom (Figure 3; the circles are not to scale). He had been fishing there several days earlier and had not seen any circles. Subsequently, after plotting the locations of the circles and the strong magnetic field on a map of the area he found that they were roughly in the direction of the sighting line of the witness and about 200 feet (60 m) from her location in the driveway (Figure 3).


Several hours later the two MUFON investigators (Bruce Morrison and Bland Pugh) arrived with a video camera and a Geiger counter. Mr. Pugh made an area search with the Geiger counter and found no clearly elevated readings. J showed them the circles at the bottom of the pond and demonstrated the operation of the gradiometer. Mr. Morrison used a video camera to record the way J operated the gradiometer as he searched the area for the presence of magnetic field sources. The video camera also recorded the audio pitch of the gradiometer as J waved it around at various locations. I subsequently determined from the videotape and from my own experiments with a nearly identical gradiometer that J operated it in a completely normal manner. A simple experiment carried out later by J at my request provided a calibration of the gradiometer and proved that it was operating normally. Mr. Morrison first recorded J operating the gradiometer on the north side of the pond (triangle location, Figure 3) looking southward toward the clump of pine trees. As J moved the gradiometer from side to side the audio pitch was maximum when the wand was pointed somewhat upward (20- 30 degrees of elevation) and generally in the direction of the trees which were about 60 feet (18 m) away across the pond. This suggested to J and the investigators that the source of the field was above the lake or perhaps at or above the treetops on the other side. As the gradiometer rod was turned away from the direction of maximum frequency (maximum gradient), i.e., rotated to the left, right, upward or downward, the frequency decreased considerably. The maximum pitch was at such a high frequency that J offered his opinion, based on using the gradiometer under many conditions for about ten years, that the response of the gradiometer was comparable to what one would get by putting the gradiometer very close to a large piece of iron or steel. The investigators then walked to the clump of pines. There the videotape shows that the highest frequency recorded, higher than at the location across the pond, was obtained when the gradiometer was vertical or nearly vertical under the trees. As J walked away from the clump of trees in various directions the maximum frequency diminished indicating that he was moving away from the field source. (Note: there was no boat available at the time, so a search was not made over the water.) A search of the area failed to turn up any source of field other than the source which seemed to be at, or above, the treetops. When J was across the pond from the trees and pointing the gradiometer toward the direction of maximum frequency the audio pitch of the gradiometer was not perfectly steady. Instead, it fluctuated rapidly by small amount in pitch ("warbled") at a roughly constant rate of about 8 - 12 Hz in a manner similar to a lightly modulated FM signal. (FM stands for frequency modulation in which a "carrier wave" of relatively high frequency is caused to change frequency slightly, usually a few percent, at a rate determined by a much lower modulating frequency.) This warbling was also apparent when the gradiometer was under the trees, where J called the attention of the investigators to this unusual effect. Subsequent experiments with a magnet (see below) created greater gradients and higher frequencies than were obtained under the trees, yet there was no "warbling" of the audio tone during the experiments. The warbling suggests that the magnetic field was pulsating slightly (changing in amplitude and/or direction) at a rate around 10 Hz. While the investigators were under the trees Mr. Morrison pointed his camera upward and videotaped the treetops and the clear blue sky. Nothing unusual was seen in the sky or on the trees. (Recorded on the videotape is a discussion by investigators in which they speculate as to whether or not the source of the field, assumed to be the UFO, was still there but "cloaked" so as to be invisible.) J repeated the area search the next day. He reported that the gradiometer had a slight response only under the trees, indicating a considerable decrease in the magnetic field gradient. Unfortunately there was no one to record these measurements of the magnetic field. On Sept. 14, three days after the sighting, the MUFON investigators returned to the area and videotaped J with his gradiometer standing under the same trees where, two days before, the audio tone was very high. Now the pitch was at a value that corresponds to "no detectable gradient." On that same day the grass circles were measured and found to be about 11 ft (3.3 m) in diameter. A week or so later the investigators thought of checking the magnetic field in the area with compasses at several locations. All the compasses pointed north indicating that there was no large magnetic anomaly in the area. (It is unfortunate that they didn't think to use compasses on the day after sighting!)


The sighting, although very brief, provided the witness with enough visual details to demonstrate that the UFO was no conventional aircraft, nor was it a bird, an insect or a piece of debris blowing in the breeze. Athough the sighting did not provide much visual data for analysis, it did provide an angular size which can be compared to the size of the circles if the distance to the UFO is assumed. The witness estimated the angular size to be about four times the diameter of the moon which corresponds to roughly 2 degrees or about 0.035 radians. If one assumes that the UFO had actually risen upward from one of the circles just before the sighting and was therefore about 200 feet (about 60 m) away, then the actual diameter of the circular object was nearly 7 feet (2.1 m). This is four feet less than the measured diameter of the circles. However a rather small increase of 1.1 degrees in the estimated angular size, making it about 3.1 degrees or six times the diameter of the moon, would make the calculated size equal the circle diameter. It certainly is reasonable to assume that the witness could have underestimated the angular size by this small amount, and hence we may conclude that the visual sighting is consistent with the size and shape of the "circular evidence" at the bottom of the pond. Of course this does not prove that the observed UFO made the circles, nor does it explain the discrepancy in number: there were three circles but only one observed UFO. The discovery of one or more circles in an area of a UFO sighting is not a rare occurence, although generally such circles are found in grass or grain growing on dry land. However, "saucer nest" circles which were discovered after a UFO sighting on January 19, 1966 near Tully, Australia, were in a swampy area. The reeds were bent below water level (Phillips, 1975; Story, 1980; Delgado and Andrews, 1989). Phillips (1975) and Delgado and Andrews (1989) describe a considerable number of UFO sightings and associated circular traces that occurred in various countries including the USA, FSU (USSR), Canada, Australia, New Zealand and Britain.


Although the UFO observation and the discovery of underwater circles are noteworthy by themselves, the aspect which really makes this case unique is the detection of the magnetic field gradient. This section presents an analysis of the field gradient data. The gradiometer is designed so that it generates an audio tone with a pitch that is very nearly proportional to the magnetic field gradient, that is, to the difference in the strengths (magnitudes) of the magnetic field at two locations. The sensitivity of the gradiometer is adjustable. In order to provide accurate gradient values corresponding to the frequencies that were recorded by Mr. Morrison during the investigation it was necessary to calibrate the gradiometer at the sensitivity level used during the investigation. At my request, J carried out an experiment which provided the data needed for calibration. I provided J with a small (1" long) bar magnet of known strength which had been calibrated with instruments at a Navy laboratory. J placed the gradiometer and magnet on a horizontal board far from any power lines or metal objects. He aligned the gradiometer wand in the east-west direction to eliminate the effect of the slight north-south gradient which is detectable with his instrument. He then aligned the axis of the magnet with the axis of the gradiometer. He placed the magnet at various measured distances from the end of the wand and tape recorded his verbal annotation of the measured distances and the resulting audio tones. The shortest distances used were 1" (2.5 cm) and 0" (0.0 cm) from the end of the rod or about 2.6" (6.6 cm) and 1.6" (4.1 cm) from the fluxgate sensor closest to the end. These produced frequencies which were much higher than those recorded under the trees near the pond. At distances of about 2 feet (about 60 cm) and beyond there was no detectable effect of the magnet. Subsequently I calculated the magnituce of the magnetic field at each fluxgate sensor for each distance of the magnet's center using the standard equation for the field of a (small) bar magnet along its axis, B = Bo/z^3, where z^3 is the cube of the distance, z, from the center of the magnet to the sensor location and Bo is the effective pole strength which was determined from the magnet calibration (1040 nanoTesla (nT) at 30 cm from either end; see the Appendix). The difference in the field amplitudes at the two sensors for any given magnet location was divided by the sensor spacing, 0.51 m, to get the gradient as a function of distance. According to the manufacturer, when the gradient is below 1,000 nT per meter (nT/m) the frequency remains at a fixed minimum of about 65 Hz. I found that above 1,000 nT/m the relation between the audio frequency and the field gradient is nearly linear, as illustrated by the calibration graph shown in Figure 4. In the frequency range of interest to this investigation, 500 - 5000 Hz, the use of a calibration factor of 12 (nT/m)/Hz provides an accuracy of 5% or better. ___________________________________________________________________________ ___________________________________________________________________________ (A note on units and conversion factors. The MKS unit of magnetic flux is the Weber (Wb), which corresponds to the number of "lines" of magnetic force around a magnet or a loop of current. The field strength or magnitude at any point is represented by the induction, called B, which is the flux per unit area, Wb/m^2, called Tesla (T). Hence when B = 1 T the magntidue of the field is 1 Wb/m^2. In the cgs system the area flux density is in Gauss (G). This is related to the MKS value as follows: 1 T = 10,000 G = 1E4 G. ["E" stands for "ten raised to the power of__"] For small fields a more typical unit is the nT = 0.000000001 T = 1E-9 T (one billionth of a Tesla) which is also called "gamma." The magnitude of the earth's field at the surface is typically about 5E-5T = 5E4 nT = 50,000 gamma which is equivalent to 0.5 G.) It is important to realize that the gradiometer does not measure the actual value of the field strength at a point in space. To measure the strength of the field one needs a device such as a rotating coil of wire (with a voltmeter attached), a "Hall effect device" or a fluxgate magnetometer that uses a single fluxgate rather than (as in the gradiometer) the difference of two fluxgates. However, the gradiometer is much more sensitive than the previously mentioned devices for measuring variations or "distortions" of the local (earth's) magnetic field caused by the presence of magnets or non-magnetized, but magnetizable, materials (e.g., iron). A magnet or a non-magnetized piece of magnetizable material will distort the local magnetic field over some distance from the piece of material, just as a rock in a river distorts the flow of a uniform stream of water. The presence of a magnet or a piece of magnetizable material in the earth's field creates a field gradient which the gradiometer can detect. A magnetic dipole consists effectively of positive (north) and negative (south) magnetic poles separated by a small distance. (Similarly, an electric dipole consists of opposite charges separated by a small distance.) Such a combination of poles creates a characteristic dipolar "shape" of the magnetic field as measured at distances from the dipole that are much greater than the separation of the poles. A small bar magnet creates such a field at distances that are large compared to the length of the magnet. A loop of wire carrying a current is also a source of magnetic field, a phenomenon which is used extensively in electromagnets, electric motors and generators. At distances considerably larger than the diameter of the loop the strength and direction of the magnetic field varies with position in the same way that it varies in strength and direction around a magnetic dipole provided that one imagines the axis of the loop (a line through the center which is perpendicular to the plane of the loop) is aligned with the axis of the analogous dipole. Hence it is common to refer to a circular loop carrying a current as a "current dipole." The similarity between a current dipole and a small bar magnet (dipole) provides a useful means for comparing the strengths of magnetic fields from different types of sources. This sort of comparison is made in this paper where calculated source strengths are given in terms of the equivalent current dipole strength which is the product of the current flowing in the wire times the area of the loop in square meters: amp-m^2. (Note: a single turn loop is assumed.) This is described more below and in the Appendix. The first field measurement as made when J waved the wand around while he was standing on the north side of the pond looking southward toward the clump of pine trees. The maximum recorded frequency was obtained when the gradiometer was pointed toward the trees and tilted upward at an angle of 20-30 degrees. The maximum frequency was about 1,500 Hz which, from Figure 4, corresponds to about 18,000 nT/m. As the gradiometer rod was turned away from the direction to the treetops the frequency decreased considerably. Next J walked to the clump of pine trees and again waved the wand around. The videotape shows that when the gradiometer was under the pine trees and pointed straight upward an even higher frequency, about 2,100 Hz, was obtained. This corresponds to about 25,000 nT/m. When the gradiometer was pointed away from the treetops the pitch was much lower, and, as J walked away from the pine trees the maximum pitch diminished. Hence it appears that he was closer to the source of the field when he was under the trees than when he was on the other side of the pond. The upward direction of the maximum gradient suggests that the source may have been at or above the tops the pine trees. However, as I have pointed out before, the gradiometer wand does not always point directly toward the source, so the source may not have been over the trees, but instead over the pond adjacent to the trees. (Note: the Journal referee of this paper pointed out that the gradiometer does not distinguish between "backwards and forwards" along the axis of the wand. Therefore, if J had made a measurement of the gradient at only a single location then one would have to allow for the possibility that the magnetic source was underground. However, the directions of the maximum gradients were measured from two locations which are about 60 feet apart. These directions intersect above ground rather than below the ground. Hence I assume that the source was above the ground.) Two days later J was recorded again standing under the trees pointing the gradiometer upward and this time the audio pitch was around 65 Hz, indicating that the field gradient had been reduced below 1,000 nT/m. (This does not mean that there was no field gradient, only that there was no gradient detectable by the instrument at the sensitivity used during the investigation.)


In the Appendix I have presented the calculation of source strengths under the simplifying assumption that the source was a single-turn current dipole as described above. This must be considered an extreme simplification of the problem because a large (infinite) number of configurations of magnetic sources (dipole and multipole sources) could create any particular gradient at a particular location. The calculation also assumes that the size of the source is much smaller than the distance from it to the gradiometer (a "point" source), whereas the actual source could have been be quite large compared to the distance. Nevertheless, this sort of calculation allows us to compare field strength associated with the UFO sighting with field strengths of known sources such as electromagnets, permanent magnets and non-magnetized but magnetizable (permeable) materials. For example, assume that the source was at some distance above the trees. If this were so, then the measured field gradient at the location across the pond, 18 m from the trees, could have been generated by a current loop of strength 3.1E6 amp-m^2 (see Appendix), providing that the axis of the current dipole was aligned with the axis of the gradiometer. This current dipole strength can be interpreted in the following way: a 1 m diameter loop, with an area of 0.78 m^2, could create the measured field gradient at a distance of 18 m if it were carrying a current of about 3.1E6 amp. Other size loops carrying other currents could also be assumed, as long as the product current-area was the same. For example, a 2 m diameter loop has four times the area and needs only one quarter of the current to produce the same field. (If there were more "turns" in the loop the current could be divided by the number of turns.) Assume, now, a 1 m diameter loop carrying the above current. At its center the field strength would be about 5 T. This field magnitude is about 100,000 times greater than that of the earth and is comparable to that inside the strongest magnetic materials (magnetic alloys such as ALNICO). Alternatively, one might imagine that the field gradient was created by the equivalent of a massive piece of magnetizable material. By comparison with the magnetic signatures of Navy ships it was determined that the field gradient measured at 18 m would be produced at a distance of about 18 m away from either end of a destroyer-sized battleship (the distance would be measured along the projected axis of the ship)! A considerably different source strength can be calculated by assuming that the source was at the tops of the trees, about 3 m above the gradiometer, when J operated it under the trees. Assuming again that the gradiometer was aligned with the axis of a hypothetical current dipole the source strength is now found to be about 3.4E3 amp-m2. This dipole strength is three orders of magnitude less than the previously calculated value because of the z^4 distance dependence of the gradient (see Appendix) and the much shorter assumed distance (3 m vs 18 m). Such a small source strength could not create the field gradient that was measured on the far side of the pond. Therefore one might assume that the actual source was considerably higher than the trees and possibly somewhat over the lake. Unfortunately there were not enough measurements made to allow even an approximate reconstruction of the magnetic field. One could imagine many (an infinite number) of configurations of magnetic field sources that could have created the measured field gradients. Therefore the most significance one can attach to these measurements is that a large magnetic field was clearly present in an area where there should have been no such field. To clarify the significance of finding such a large field, consider the following facts: (a) wood is not ferromagnetic (it cannot be magnetized); (b) while J was standing under the trees with his gradiometer pointed upward and generating a high pitch on Sept. 12, Bruce Morrison was videotaping the tops of the trees which were silhouetted against a clear blue sky and the investigators could see nothing up there that could cause such a field gradient; (c) if, somehow, the wood had been made ferromagnetic by a UFO (an impossibility, according to the physics of magnetic materials), or if the UFO had deposited a massive amount (hundreds of pounds?) of some ferrous (i.e., containing iron) material on the trees (no deposit of material was seen on the trees, however), then the strength of the magnetic field should have been the same on the second day of the investigation because ferrous materials do not lose their magnetism at environmental temperatures (they do lose it at temperatures of many hundreds of degrees); (d) there had been rain the night after the sighting, yet there was no indication of magnetic sources on the ground, so no magnetic residue had washed off the trees. Although the gradient was large there was no observable effect on the videocamera. A calculation of the field strength at the videocamera when it was under the trees, assuming that the source was farther than about 10 ft (3 m) away (at or above the tops of the trees) shows that the field from a 3.4E3 amp-m^2 source would have been 0.00003 T or less, which is much too low to affect the videocamera mechanism or the videotape. Hence we are left with a double mystery: (1) how did the field get there in the first place, and (2) once there, why did it disappear?


Anomalous magnetic effects have long been associated with UFOs. The earliest magnetic effect report on record is that of Fred Johnson who was prospecting near Mt. Adams on June 24, 1947. On that day, and only minutes before Johnson's sighting, Kenneth Arnold, a private pilot was flying a small plane about 20 miles west of Mt. Rainier in the state of Washington. Arnold saw nine flat, shiny crescent-like objects fly southward past Mt. Rainier (Maccabee, 1986; Story, 1980). Arnold last saw them as they vanished in the distance near Mt. Adams, about 50 miles south of Rainier. Arnold's sighting was widely reported in the press and gave rise to the term "flying saucers." (Although the Air Force called Arnold's sighting a "mirage," and others have offered similar suggestions, the fact is that Arnold's sighting could not have been caused by atmospheric phenomena. It has never been explained (Maccabee, 1986).) Several weeks after the sighting Johnson told the Air Force and then the FBI that he saw several of the objects fly overhead. He looked at them with a telescope and estimated their altitude as about 1,000 ft (about 300 m) above him and their diameter at about 30 ft (about 9 m). Of particular interest here, however, is Johnson's statement that, as the object passed over, his compass continually oscillated from side to side (Maccabee, 1986). Assuming that the "saucers" were the source of the magnetic field that caused the compass to oscillate we can estimate the source strength in the following way. Assume that a magnetic field with a strength roughly 1/5 of the earth's field (i.e., about 10E-5 T) that oscillates in direction or pulsates in amplitude (or both) could cause a noticeable oscillation of a compass needle. For simplicity also assume that a flying saucer is effectively a current dipole 9 m in diameter and that the compass was, at least part of the time, at a distance of 300 m along the axis of the dipole as each saucer flew over. Since 300 m is much greater than the radius, 4.5 m, Eq. 2 in the Appendix can be approximated as B = 2 Bo/z^3. Inverting this equation and solving for Bo with B = 1E-5T and z = 300 m yields Bo = 135 T-m^3 which corresponds to a source strength of 1.35E9 amp-m^2. This source strength can be created by a current of about 21 megamps flowing in a loop 9 m in diameter. The field strength at the center of the loop would be about 3 T. Of course, these very simplified calculations probably do not provide us with the actual effective source strength of the saucers, but they do demonstrate that the fields would have been very large to have affected Johnson's compass from a distance of 300 m. In the years following 1947 there were reports of UFOs affecting iron items such as streetsigns and automobiles (Rodeghier, 1981). Researchers have long felt that car-stopping events were associated with the presence of large magnetic fields in the presence of UFOs, although evidence for this has been indirect at best. Experiments have shown (Rodeghier, 1981) that either a steady or a pulsating magnetic field can affect a spark coil in an automobile ignition system. A steady magnetic field can saturate the magnetic core of the coil and decrease the spark strength. A strong enough field could kill the spark completely. A somewhat weaker field which is pulsating at roughly the firing frequency of the automobile but is out of phase with the firing can cause the engine to stall. The demonstrations of the effects of magnetic fields on automobile ignition systems are interesting, but they do not provide conclusive evidence that magnetic fields associated with UFOs have stopped any cars. Claude Poher, a French scientist formerly associated with the French National Space Agency (CNES), studied sightings in France that occurred during the October, 1954 "flap." He also studied magnetic field readings at a geophysical research station located at Chambon-la-Foret (Hendry, 1979). Poher claimed that the strength of the magnetic field tended to be larger during the flap, although Hendry (Hendry, 1979) has pointed out that this does not prove that the increase was caused by UFOs since the earth's magnetic field tends to fluctuate anyway. (The fluctuations are typically of a magnitude around 0.0001 to 0.001 of the earth's field and are a result of fluctuations in the "solar wind.") Poher also claimed to find a correlation between the distance of a reported object from the station and perturbations in the vertical component of the magnetic field at the station (Hendry, 1979; Hynek and Vallee, 1975). A graph of Poher's magnetic field data (Hynek and Vallee, 1975) has been magnified, slightly redrawn and reproduced in Figure 5 for convenience in the following discussion. _________________________________________________________________________ _________________________________________________________________________ Poher found that the strength of the perturbations seemed to decrease inversely with the distance of a UFO sighting from the station (the greater the distance, the smaller the effect). Unfortunately the closest distance was still 30 km away so the mathematical relation that he derived from the data was not well tested. Furthermore, although it was not pointed out in the publication, the line that he drew through the data points shows an inverse square decrease with increasing distance rather than the expected inverse cube which is associated with typical dipolar magnetic fields. If the data were really accurate, this could be considered to be evidence that UFOs are associated with monopolar magnetic fields. The idea that there might be magnetic monopoles is, so far as we know, only a theoretical construct which symmetrizes the Maxwell equations of electrodynamics by providing a monopolar source for magnetic fields which is analogous to the source (electron, proton) of the monopolar electric field. All sources of magnetic field of which we are experimentally aware are dipolar (or multipolar) in nature. Hence I have drawn another line, which corresponds to the inverse cube dipole field, through Poher's data. It is interesting to note that the inverse cube decrease with distance does not fit the data as well as the inverse square. However the better fit for the inverse square should not be considered as valid evidence that UFOs are sources of monopolar magnetic fields because range in distances is quite limited (one would like to see data from ranges 1 - 10 km) and because the data points are very scattered. By projecting the inverse cube lines on Figure 5 "backward" to a distance of 1 m from an assumed source one can show that the equivalent dipole strength is about 1.5E13 amp-m^2 which is many orders of magnitude greater than the previously calculated values. Since the magnitudes of these source strengths are crucially dependent upon the accuracy of the data points in Poher's graph, the numbers calculated here can be considered to be no more than indicative of very strong fields associated with UFOs, assuming that Poher was correct in associating these fluctuations with UFO sightings. A visual observation by Wells Allan Webb (reported in _Mars, the New Frontier_, 1956; reproduced in "The UFO Evidence," NICAP, 1964, R. Hall, Ed.) may also be related to a magnetic field around a UFO. He reported that on May 5, 1953 between 9:45 and 10:0 AM he was observing the sky near the Yuma Air Force Base in Arizona. Beside the normal Air Force craft flying around he also noticed, in the northern sky, "...what at first appeared to be a small white cloud... the only one in the sky at the time." However, it was not a cloud. It was at an elevation of about 45 degrees, initially, and it moved about "30 degrees to the east" during the first 5 minutes of his observation. It appeared "oblong with the axis in the horizontal plane." Then, "it appeared to abruptly turn and travel northward; at the same time it's oblong shape changed to circular section. As a circular object it rapidly became smaller as if receding. While receding it did not lose any of its apparent brightness. In about 30 seconds of this, its diameter became too small for the author to hold in his vision." What makes this sighting interesting from the magnetic perspective is what Wells reported seeing through his polaroid glasses. He wrote, "The author was wearing Polaroid glasses having a greenish tint and, as was his custom when studying clouds, he took the glasses off and put them on at intervals to compare the effect with and without Polaroid." During the first 5 minutes or so of observation he noticed no special effects of the polaroid glasses. However, after the object turned, "...several uniformly spaced concentric circles appeared around the now circular object" when viewed through the polaroids. "The circles were distinct dark bands which enveloped the silvery disc. The largest of these circles was, perhaps, six times the diameter of the central disc. When the writer removed the glasses the disc remained but the concentric rings vanished. When the glasses were put on again the rings reappeared. The writer repeated this several times, each time with the same result. The rings with glasses on faded to invisibility before the disc became too small to see." So, what does this sighting have to do with a magnetic field? The answer is the property of strong magnetic fields to cause substantive media including gasses (air) to rotate the plane of polarization. Since Mr. Wells was looking northward (roughly perpendicular to the direction to the sun) in the morning, a sizeable fraction of light reaching his eyes from the clear sky was polarized (hence the value of polarizing glasses, to cut glare by reducing the amount of polaroized light). Polarized light passing close to the object before reaching Mr. Well's Polaroid glasses could have been effected by a magnetic field on the object. More specifically, the field could have rotated the plane of polarization by varying amounts, with the lowest amount being for light farthest from the object but which is still within a strong field. As the plane of polarization was rotated by varying amounts some light would pass the polaroid glasses (because it has been rotated such that it aligns with the polarization direction of the glasses, i.e., horizontal) and some would be blocked (not enough rotation or too much rotation). Whether the polarized skylight was passed (bright ring) or blocked (dark ring) would depend upon how close it passed to the object. Because the rotatory power (Verdet constant) for air is very low the magnetic field would have to be huge to cause this effect. Turning to a different but related matter, many people have attempted to detect UFOs using simple magnetic field sensors in the past. A typical simple sensor is a compass with an optical system designed to detect any motion of the pointer from its normal north-south direction, and to set off an alarm. I am aware of no clear-cut successes of this approach to detecting UFOs. On the other hand, sensitive magnetic field detectors that might detect UFOs are not common items easily available to civilian UFO investigators and very few, if any, have them available for sighting investigations. I am aware of only one other magnetic site survey of an area of UFO activity that is similar to the one reported here (Bruce Cornet, private correspondence, 1993: Dr. Cornet, a geologist, has surveyed an area of UFO activity near Pine Bush, New York, using a proton magnetometer.) The success in detecting a field after the sighting reported here and the past reports of apparent magnetic effects suggest that local UFO groups in areas of continued activity, perhaps with monetary aid from national UFO organizations, should consider purchasing these devices for use by trained field investigators along with the standard equipment (cameras, video cameras, sample taking devices, etc.).


Following a brief visual sighting of a disk shaped UFO an area search was made. In the bottom of a shallow pond three 11 ft circles of depressed pond grasses were discovered. An estimate of the size of the disk based on the visual apparent size and the distance to the circles agrees reasonably well with the size of the circles. An area search was made with a magnetic field gradiometer. The search discovered locations of anomalously high field gradient in the absence of known sources (large pieces of metal or electric current carrying wires). Estimates of the magnetic source strengths were made using the recorded gradiometer data (audio tones). The source strengths were found to be quite large in a manner that is consistent with estimates based on observed magnetic phenomena associated with other UFO sightings. One major difference between this magnetic field detection and other reported cases is that there was no UFO visually present during the detection of the field, which was only detected many hours after the sighting. This raises the question of whether or not a UFO actually was present during the measurements but in some way made itself invisible, or if the departing UFO in some way managed to leave a magnetic "trace" of its presence many hours before. (Perhaps there were still a bunch of not-yet decayed-or blown-away magnetic monopoles stuck in the treetops. :) ) I thank Mrs. A and the Gulf Breeze Research team members (Bruce Morrison, Bland Pugh and David Holcomb) for providing me with information needed to complete this analysis. I also thank J for having the presence of mind to use his gradiometer during this investigation and for carrying out the calibration tests. Finally, I thank the referees for helpful comments on this paper.


A "field" is a volume in space throughout which some quantity (or quantities) varies in a consistent and measureable way. The magnetic field varies in both magnitude and direction (i.e., it is a vector field) in a volume of space around a magnet or around a loop of current. As virtually any textbook on electromagnetic theory (e.g., Scott, 1959) shows, the field of a magnetic dipole (or an electric dipole), because of its rotational symmetry about the axis of the dipole, can be represented in vector notation most simply by using cylindrical coordinates with the z axis along the axis through the center of the magnet or perpendicular to the plane of the current loop. The other two axes, x and y, are replaced by new axes which are the radial distance, r, from the center of the dipole, and the angle, a, between r and the positive z axis. The equations for the radial and angular vector components of B, Br and Ba, are 2Bo cos(a) Bo sin(a) (Br,Ba) = ( ----------, ----------) 1) r^3 r^3 where the magnitude of the field is given by (Br^2 + Ba^2)^1/2 and r is assumed to be much larger than the dimensions of the source of the field (much greater than the length of a magnet or the diameter of a current loop). In this equation Bo in T - m^3 is given by (1E-7)MSL if the source is a bar magnet of magnetization per unit volume M (amp/m) with cross- sectional area, S (m^2) and length, L (m), or Bo is (1E-7)IS if the source is a current loop (a single turn) of area S and current I (amp). Figure A1 illustrates the coordinate systems for the two types of sources. ________________________________________________________________________ ________________________________________________________________________ If the source is a current loop a more correct equation for the field along the z axis where a = 0 is 2Bo Br = ---------- 2) (z^2+R^2)^3/2 where R is the radius of the loop and Bo = (1E-7)IS. Along the z axis sin(a) = 0 in Eq. 1 so there is no angular component of B: B points either directly toward or away from the center of the source at all z values. Comparing Eq. 1 with Eq. 2 we see that r has been replaced by z. When z is much greater than R the equations are essentially equal. The simple dipole model can be used to calculate the equivalent source strength, Bo, from the gradient measured by J's instrument if the distance to the source is known or assumed. The measured gradient of the field is the derivative of B along the axis of the wand. In terms of the dipole model it can be shown that (by far!) the simplest direction to take is along the z axis (i.e., assume that the wand axis lies along the z axis). Also assume that the field gradient is measured at a distance far from the source (z >> R) so that R can be ignored in Eq. 2. Then straightforward differentiation gives the magnitude of the gradient as |dB| 6 Bo ---- = --------- . 3) |dz| z^4 This equation can be inverted and solved for Bo as a function of the measured gradient: z^4 |dB| Bo = ------ ---- . 4) 6 |dz| When J was on the far side of the pond he was about 18 m from the trees. The measured gradient when J pointed the gradiometer toward the treetops was about 18,000 nT/m. If we assume that the source was a current loop at the distance of the trees with its axis pointing toward J when he stood on the far side of the pond, then the measured gradient multiplied by z^4 and divided by 6 gives Bo = 0.31 T - m^3. Using the definition Bo = 1E- 7IS, the equivalent current dipole source is found to be IS = 3.1E6 amp - m^2. With this dipole strength we can use Eq. 2 to calculate the field at the center of a loop. Assume that the loop has a radius of 0.5 m. Then, at z = 0, B = 2 x 0.31/0.5^3 = 5 T. A field this strong is comparable to saturation field strengths inside the strongest magnets. When J stood under the trees he obtained a frequency that corresponds to about 25,000 nT/m. Assuming that the source was at the treetops or just above, at a distance of 3 m, Eq. 4 yields Bo = 3.5E-4 T - m3, which is much lower than the previously calculated value. This large decrease results from the assumption of a short distance (3 m vs 18 m) combined with the fourth power distance dependence of the gradient. In this case the current loop strength is 3.4E3 amp - m2 which is still quite large. If one makes the reasonable assumption that the source strength should have been the same for both measurements then one must abandon the assumption that the source was above the trees. Using Eq. 4 with the two values of |dB/dz| to calculate the ratio of the z distances we find (z2/z1) = (dB1/dB2)^1/4 where z1 is the distance from the first measurement location and z2 is from the second (trees). The ratio is (18,000/25,000)^1/4 = 0.92 which means that the source would have been about equidistant between the measurement locations (z2 = 0.9 z1) and hence at some height above the pond. Alternatively the source had a complicated field configuration which gave rise to the measured gradients. The text makes a passing mention of the possibility that monopoles might be involved. It is amusing to calculate the source strength if the source were actually monopolar (a collection of monopoles) with magnetic charge Qm. In this case it makes no sense to compare the strength to a current dipole (a loop of wire carrying a current, as above). The field at distance r from the center of the monopolar source is B = Bo/r^2, where Bo is T - m^2. Therefore the magnitude of the gradient is |dB/dr| = 2Bo/r^3 so Bo = r^3|dB/dr|/2. This is the monopolar analogue of the dipolar Eq. 4, above. From this equation we can calculate Bo for r = 18 m and |dB/dr| = 18,000 nT/m: Bo = 0.05 T-m^2. Similarly for r = 3 m and |dB/dr| = 25,000 nT/m, Bo = 0.0003 T-m^2. The latter two calculations assume the source was over the trees and yield different values of Bo. The same Bo value can be obtained for both calculations if the assumed radial distances are adjusted appropriately, as was done above for the dipolar source: r1^3|dB1/dr| = r2^3|dB2/dr| or r2/r1 = (dB1/dB2)^1/3 = 0.9 where r1 is the distance from across the pond and r2 is the distance from the trees. This calculation says that the assumed monopolar source would have been at some altitude and almost halfway between the two measurements locations (r2 = 0.9 r1). The implications of these calculations are discussed in the text. *********************************************************************** * This paper was first presented at the Washington, D.C. Annual Meeting of the American Physical Society in April, 1993


Delgado, P. and Colin Andrews, Circular Evidence, Phanes Press, Grand Rapids, Michigan (1989) Hendry, A., The UFO Handbook, Doubleday and Company, Garden City, New York (1979) Hynek, J. and J. Vallee, The Edge of Reality, Henry Regnery, Chicago, Illinois (1975), pp. 86-87 Maccabee, B., "Still in Default," in the Proceedings of the 1986 MUFON International Symposium, pp. 131-160; published by the Mutual UFO Network, Seguin, Texas (1986) Phillips, T., Physical traces associated with UFO Sightings, published by the Center for UFO Studies, Chicago, Illinois (1975) Primdahl, F., "The Fluxgate Magnetometer," Scientific Instruments, Journal of Physics E 12, pp. 237-332 (1979) Rodeghier, M., UFO Reports Involving Vehicle Interference, published by the Center for UFO Studies, Chicago, Illinois (1981) Scott, W., The Physics of Electricity and Magnetism, Wiley and Sons, New York (1959) Shoenstedt Instruments Corp., "Operator's Manual for the GA-52 Magnetic Locator," Reston, Virginia Story, R., The Encyclopedia of UFOs, Doubleday and Co., Garden City, New York (1980)