Robert A. Helliwell[1] (September 2, 1920 – May 3, 2011) was an electrical engineer and professor at Stanford University. He was one of the pioneering scientists in the study of whistlers and related ionospheric phenomena.
Early life
editHelliwell was born in Red Wing, Minnesota, on September 2, 1920. He and his mother moved to Palo Alto, California after his father died. Helliwell and his wife, whom he knew in high school, were both undergraduates at Stanford University.[2]
Career
editHelliwell was associated with Stanford University for his entire career, receiving all his academic credentials there and becoming a member of the electrical engineering faculty in 1946. Helliwell received his AB degree in 1942, a combined MA and electrical engineering degree in 1944, and his PhD in 1948.[3]
Whistlers
editHelliwell's greatest discovery was accidental, as is often the case in science. Helliwell and one of his students, Jack Mallinckrodt, were investigating lightning noise at very low radio frequencies at Stanford University in 1950. Mallinckrodt heard some whistling sounds and brought them to Helliwell's attention.[2] As Helliwell recalled in an article in the October 1982, issue of the Stanford Engineer, he thought it was an artifact, but he stood radio watch with Mallinckrodt until he heard these whistlers for himself. Helliwell described these sounds as "weird, strange and unbelievable as flying saucers" in a 1954 article in the Palo Alto Times.[2]
Research
editIn true scientific fashion, Helliwell tried to understand the mechanism involved in the production of whistlers. He conducted experiments at the VLF outpost, Siple Station in West Antarctica, which was active from 1971 to 1988.[2] Since the wavelength of VLF radio signals is huge (a frequency of 10 kHz corresponds to a wavelength of 30 kilometers, or 18.64 miles), the Siple Station had an antenna that was thirteen miles long. The antenna was used to transmit VLF radio signals into Earth's magnetosphere, to be detected half a world away in Canada. It was possible to inject these signals into the magnetosphere, since the ionosphere is transparent to these low frequencies.[2]
Writings
editHelliwell was the author of one book, "Whistlers and Related Ionospheric Phenomena," and more than 90 scientific papers.[2] Three of his papers deserve special mention. One of these reported on low frequency emissions associated with the 1989 Loma Prieta earthquake.[4] Another describes how injection of a low frequency radio signal into the magnetosphere causes a radio quieting of the natural noise that's associated with these frequencies.[5] Another paper showed that the alternating current power grids in North America (60 Hz) and Europe (50 Hz) affect auroral chorus emissions.[6]
Honors
editHelliwell was a fellow of the Institute of Electrical and Electronics Engineers and the American Geophysical Union, and a member of the American Association for the Advancement of Science and the United States National Academy of Sciences.[7] The National Science Foundation named a range of hills in Antarctica, along the coast of Victoria Land on the Ross Sea, the Helliwell Hills in his honor.[2][8]
See also
editReferences
edit- ^ "Robert Helliwell (Sept. 2, 1920 – May 3, 2011) – Stanford VLF Group".
- ^ a b c d e f g Melissae Fellet, "Robert Helliwell, Radioscience and Magnetosphere Expert, Dead at 90," Stanford Report, May 20, 2011 at http://news.stanford.edu/news/2011/may/robert-helliwell-obit-052011.html
- ^ Electrical Engineering Prof. Helliwell Dies at 90, Stanford Daily News, May 24, 2011 at http://www.stanforddaily.com/2011/05/24/electrical-engineering-prof-helliwell-dies-at-90/
- ^ A. C. Fraser-Smith, A. Bernardi, P. R. McGill, M. E. Ladd, R. A. Helliwell, and 0. G. Villard, Jr., "Low Frequency Magnetic Field Measurements Near the Epicenter of the M 7.1 Loma Prieta Earthquake," Geophysical Research Letters, vol. 17, no. 9 (August, 1990), pp. 1465-1468 at "Archived copy" (PDF). Archived from the original (PDF) on 2011-09-28. Retrieved 2011-06-18.
{{cite web}}: CS1 maint: archived copy as title (link) - ^ R. Raghuram, T. F. Bell, R. A. Helliwell, and J. P. Katsufrakis, "A Quiet Band Produced by VLF Transmitter Signals in the Magnetosphere," Geophys. Res. Lett., vol. 4, no. 5 (May, 1977), pp. 199-202 at "Archived copy" (PDF). Archived from the original (PDF) on 2011-09-27. Retrieved 2011-06-18.
{{cite web}}: CS1 maint: archived copy as title (link) - ^ J. Luette, C. Park, and R. Helliwell, The Control of the Magnetosphere by Power Line Radiation, J. Geophys. Res., vol. 84, no. A6 (June, 1979), pp. 2657-2660 at http://nova.stanford.edu/~vlf/publications/220.pdf
- ^ Robert A. Helliwell, Professor Emeritus of Electrical Engineering, Stanford Personal Web Site at "Robert A. Helliwell". Archived from the original on 2007-06-13. Retrieved 2007-05-07.
- ^ Listening in on lightning, Stanford Engineering Web Site at "Stanford School of Engineering - Engineering memory of the month". Archived from the original on 2011-10-25. Retrieved 2011-06-18.
Further reading
edit- Whistlers and Related Ionospheric Phenomena, Robert A. Helliwell, Stanford University Press, Stanford, California, 1965.