Antony C. Fraser Smith, Research Interests

A. C. Fraser-Smith: Research Interests

[Note: Clicking on any one of the highlighted references below will give you a segment of Prof. Fraser-Smith's publication list with the desired reference usually at (or close to) the top of the segment.]

Prof. Fraser-Smith conducts experimental and theoretical research into the origin and properties of low frequency electromagnetic field variations in the Earth's environment and in space. The specific frequencies covered by this work are the following:

ultra-low frequencies (ULF; frequencies less than 5 Hz),
extremely-low frequencies (ELF; frequencies in the range 5 Hz - 3 kHz), and
very-low frequencies (VLF; frequencies in the range 3 - 30 kHz).

Prof. Fraser-Smith also investigates the relation of these ULF, ELF, and VLF electromagnetic variations to other phenomena on and below the Earth's surface (including the sea surface), in the neutral atmosphere, and in the ionosphere, magnetosphere, and interplanetary space.

Figure 1, displayed below and taken from [ Fraser-Smith and Roxburgh,1969 ], shows a spectrogram (i.e., a frequency versus time display) of very simple ULF magnetic signal. During the 1960's these signals were referred to as hydromagnetic (hm) whistlers. Nowadays they would be called Pc 1 whistlers. Notice how each successive element of the signal is progressively more inclined to the time axis. The straight lines drawn in on the figure show how the authors made use of the progressively increasing inclination of the whistler's elements to estimate the starting time of the whistler event.

Prof. Fraser-Smith's research on low frequency electromagnetic field variations in the Earth's environment included the first measurements of ULF geomagnetic field fluctuations with a superconducting magnetometer [Fraser-Smith and Buxton,1975 ] and it has led to a number of new discoveries:

the DC-powered Bay Area Rapid Transit (BART) system is a prolific source of ULF magnetic field variations throughout the San Francisco Bay area and beyond [Fraser-Smith and Coates,1978],
there is a "weekend effect" in many geomagnetic phenomena, indicating some influence from man's activities [Fraser-Smith,1979],
trees can be used as ULF antennas (as shown at the right, a Stanford oak tree appeared on the cover of Nature as a result of this work; click on the image for magnified version) [ Fraser-Smith,1978],
thunderstorms are a major source of ULF magnetic field fluctuations [Fraser-Smith,1993], and
there may be ULF magnetic field precursors to moderately-large and large earthquakes [Fraser-Smith et al.,1990; Bernardi et al.,1992].
In addition to the above, a new variety of geomagnetic pulsation event (a "chevron structured" Pc 1 pulsation event) was identified and named [Fraser-Smith,1977].

A relevant current activity in this area of low-frequency electromagnetic field research is Prof. Fraser-Smith's involvement (as Principal Investigator) in the following project:

(a) a project to measure the global distribution of ELF/VLF electromagnetic noise using a network of eight Stanford-designed (and constructed) measurement instruments. This project is sponsored primarily by the Office of Naval Research but it also receives logistics support from the National Science Foundation for the Arctic and Antarctic instrumentation and it has also received substantial support from the U.S. Air Force's Rome Laboratory. Measurement systems, called ELF/VLF radiometers, are being operated at Stanford University; Arrival Heights, Antarctica; and Sondrestromfjord, Greenland.

During the decade of the 1990's, Prof. Fraser-Smith was heavily involved in the earthquake detection project described just below. However, as time progressed it became clear that the project was unsuitable for students, since it was dependent upon measurements made in conjunction with earthquakes and earthquakes, unfortunately, do not necessarily cooperate with researchers. Furthermore, the project required continual fund-raising and funds for the continual operation and maintenance of equipment were difficult to obtain. Thus, in the decade of the 2000's, Prof. Fraser-Smith largely terminated his active involvement in the project. Here is a description of this now terminated project:

(b) a project attempting to measure ULF magnetic signals prior to further earthquakes in California. Independent ULF measurements systems were installed at the Varian and Haliburton ranches near Parkfield in Central California, where an earthquake with a magnitude greater than 6 was expected in the "near" future, and at Piñon Flat and Table Mountain in Southern California.

The above systems were all installed on or close to the San Andreas fault. When combined with the system originally installed at Corralitos, just south of the San Francisco Bay area, they enabled ULF magnetic field fluctuations along a substantial section of the San Andreas fault to be monitored (see map of earthquake measurement sites). An additional two measurement systems were then installed along the Hayward Fault at Mission Peak and Lake Chabot on the east side of San Francisco Bay, and another was installed on the west side of San Francisco Bay in Stanford University's Jasper Ridge biological preserve, close to the segment of the San Andreas fault that gave us the great San Francisco earthquake of 1906 (and which, ominously, has not moved since that time). The map of earthquake measurement sites shows the locations of all these measurement sites and their relation to the San Andreas fault. The measurement program was supported primarily by the U.S. Geological Survey; the Hayward fault installations were supported by EPRI and Stanford supported the Jasper Ridge installation.

Fraser-Smith et al.,1990

Fraser-Smith and Coates,1978

T. T. Liu, "Ultra-Low Frequency Magnetic Fields in the San Francisco Bay Area: Measurements, Models, and Signal Processing," Tech. Rept. D180-2 , STAR Laboratory, Stanford University, EPRI Grant WO8035-2 and USGS Grants 1434-HQ-97-GR-03124 and 1434-HQ-96-GR-02715, June 1999.

Prof. Fraser-Smith has also been involved for some time in studies of the artificial generation of low-frequency electromagnetic waves, which can be used for active experiments in the Earth's upper atmosphere and for communication. One result of this work was the first use of a peninsula (on Chappaquiddick Island) as an antenna [Fraser-Smith and Villard,1980 ].

A relevant activity in this area of research was Prof. Fraser-Smith's involvement in a project, sponsored by the Rome Laboratory of the U.S. Air Force, to investigate the possible use of electron beams in space as low-frequency antennas. This work has led to an active involvement in electron beam experiments on the Space Shuttle and on rockets [e.g., Banks et al.,1990; Raitt et al.,1995].

He also participated in the two Tethered Satellite System (TSS) missions of the Space Shuttle and their associated Shuttle Electrodynamic Tether System (SETS) experiments, since a 20--100 km long conducting tether in space could be a remarkably efficient antenna for the generation of low-frequency electromagnetic signals in space. Two graduate students, Victor Aguero and Scott Williams obtained their Ph.D.'s while working on this project.

In addition to the above activities, Prof. Fraser-Smith has the following related interests:

He studies the generation, propagation, and reception of ULF, ELF, and VLF electromagnetic signals in the sea, with particular application to submarine communication and detection. A relevant activity in this area of research was Dr. Fraser-Smith's involvement (with Professor O. G. Villard, Jr.) in a project, sponsored by the Office of Naval Research, to develop an index of natural ULF magnetic noise that can be used as an indicator of the noise levels that are likely to be encountered during undersea communication and detection [Bernardi et al.,1989]. It was this project that led to the fortuitous measurement of large-amplitude ULF magnetic signals at Corralitos, California, before the large Loma Prieta earthquake of 1989 [Fraser-Smith et al.,1990].
Most recently, he identified 82 Hz signals from a Russian Navy transmitter on the Kola Peninsula and measured their amplitude out as far as the transmitter's antipodal point, which is located in the sea off the coast of the Antarctic. These measurements were the first ever made of a man-made ELF signal at such great distances, and, with the help of Peter Bannister, a colleague, they were used to carry out the first experimental test of the propagation theory for ELF signals at great distances. The theory did very well. [Fraser-Smith and Bannister, 1997].

He participated in studies of the biological effects of low-frequency electromagnetic fields. Appointed (after examination by both the Environmental and Electric Power Agencies of the State of New York, and by the public) to a N.Y. State scientific advisory panel charged with overseeing an extensive research contract program (budget: $5,000,000) to determine whether exposure to the electromagnetic fields of overhead electrical power transmission lines is hazardous to human health. The final report of this panel was issued on 1 July 1987. Since he is not a biologist, Dr. Fraser-Smith generally only participates in these studies to the extent that he can comment on the electric and magnetic field exposures. [Ahlbom et al.,1987].

He also participates in studies of high frequency (HF) radio wave propagation, with particular emphasis on (a) the systematics of round-the-world (RTW) propagation [e.g., Bubenik et al, 1971] and (b) the effects of geomagnetic disturbances.

Finally, Prof. Fraser-Smith has long had an interest in the dipole models of the Earth's magnetic field and in the locations the north and south "geomagnetic" poles predicted by these models. He has published a definitive study of the eccentric dipole model of the Earth's magnetic field [Fraser-Smith,1987].

Remember that the references quoted can be found in Prof. Fraser-Smith's publication list.

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