SOME PERSONAL RECOLLECTIONS OF EARLY BEGINNINGS IN SPACE AND ATMOSPHERIC SCIENCE
A. Vallance Jones
[See also related material in the transcript.]
This contribution is adapted from a talk I gave a few years ago on my scientific activities in Canada. It contains material that is relevant to some early developments in the field but certainly only a small part of the story.
I arrived in Canada in 1949 to take up a post-doctoral fellowship in Dr. Herzberg' laboratory at NRC in Ottawa. This period was an exciting one. There were regular meetings in Herzberg's office and members of the group gave regular seminars on topics of which they found of interest. One exciting aspect of the laboratory was the procession of outstanding people who came to visit and usually to give a talk on their work. One such visitor was David Bates who gave a most interesting seminar on upper atmospheric chemistry. His ability to quote reaction rate constants and concentrations to discuss the probability of various processes in the ionosphere really excited my interest in the subject. Sydney Chapman was another distinguished visitor who contributed to my interest in the upper atmosphere. Perhaps most influential of all was a talk given by another PDF, Mike Feast who had developed an interest in the spectra of aurora. I remember this seminar well, with it discussion of the features identified in the aurora, Vegard's work on measuring temperatures from molecular band profiles Meinel's new work on Doppler shifted hydrogen lines in aurora as well as the new N2+ band system which bears his name. About that time Herzberg became interested in the OH bands discovered in the infrared nightglow by Meinel and the possibility of finding these bands further into the infrared. However, I heard that Dr. Petrie at Saskatoon was looking for a Research Associate to explore the infrared spectrum of the aurora as part of a contract which he had received from the U S. Air Force for studies in aurora and airglow. Petrie had already hired Don Hunten to work on this project so it was arranged that I would take up this position in February 1952 after returning from a honeymoon visit home to New Zealand.
So it was that on frigid clear morning in February, that I alighted from the CNR "Continental" at the CN station in Saskatoon. It was a somewhat inauspicious arrival since due to some mix-up there was no one to meet me and there I was at the crack of dawn carrying my bags up 21st St. looking for somewhere get out of the cold. I checked in at a somewhat dilapidated hotel to await a civilized hour to telephone my new employer. Finally I got through to Dr. Harrington, the head of the Physics department. He was instantly very helpful and came to pick me up and drove me out to the university. After a somewhat alarming drive on slippery snow covered streets, we made it safely to the Physics Building.
From this point everyone was very kind and helpful. Dr. Petrie had in fact been making arrangements to move to a position with DRB in Ottawa and by spring he departed leaving Dr. Currie to take over the USAF contract and myself and Dr. Hunten to carry on research for the project.
On our final move west we visited Ralph Nicholls in London, Sutherland in Ann Arbor and Meinel at Yerkes before beginning the long trip across the U.S. and Canadian praires to Saskatoon. We were impressed by the long straight roads with only the grain elevators protruding above the level plain every 10 miles.
So began an exciting period of about 16 years in Saskatoon where a great deal of time was spent in teaching and doing research on airglow and aurora taking advantage of the techniques learned in Sutherland's and Herzberg's laboratories. The contributions of a number of excellent Saskatchewan graduate students was of great importance. First there was Herb Gush who did a remarkable job in building an infrared grating spectrometer equipped with a PbS detector to get the first spectra of the OH bands of the nightglow in the 1-2m region. This work was continued by Tony Harrison, Jim Read, Don Shemansky and Dick Gattinger who continuously improved the instrument and succeeded in obtaining better airglow spectra as well as the more elusive 1-2m spectrum of the aurora. After leaving Saskatoon, Herb Gush obtained very much improved nightglow spectra using Fourier transform spectroscopy from the ground and also from balloons at longer wavelengths. A major attempt to apply this method to the auroral spectrum was made by Earl Fjarlie who built a Michelson interferometer for this purpose around 1964. Excellent nightglow spectra were obtained but the aurora refused to co-operate by the time the instrument was ready. Perhaps the most significant result of this work was the discovery of the 1.58 micron IR Atmospheric band of O2 in twilight spectra obtained by Tony Harrison and the subsequent demonstration by Dick Gattinger that this band is produced by the photo-dissociation of O3. Our exploration of the IR spectrum, led to some additional support for an attempt to extend the study beyond 2 microns and the arrival of a research associate, newly graduated from Harvard by the name of John Noxon. John was a remarkable person, brilliant as an experimenter and in the interpretation of results. He was also a Himalayan climber, accomplished organist and friend. When it became clear that the longer wavelength spectrum of the airglow and aurora could be not be studied from the ground we built a balloon-borne spectrometer which was flown at Valcartier with the co-operation of Bob Lowe and John Hampson. This partially successful experiment kindled our interest in balloon and aircraft borne instruments. This led eventually to discovery by John Noxon that the much stronger 1.27 micron IR Atmospheric band could be observed easily both in the airglow and the aurora from balloon and aircraft heights. About this time, Wayne Evans, a new graduate student became interested in balloon photometer measurements of the 1.27 micron band at the same time as Ted Llewellyn came to work with us on these problems. Ted's enthusiasm and organizing abilities soon resulted in our mastering the technique of flying balloon payloads from the Saskatoon area. Suffice it to say that balloon and later rocket-borne measurements of the 1.27m band provided a good understanding of the excitation of this emission which subsequently has become the basis of a major method for studying higher level O by balloon, rocket and satellite. There were a number of other lines of research such as the higher resolution photographic spectra of aurora and the studies of the time-latitude distribution of proton and electron aurora carried out by Ted Montbriand and Rudy Wiens which were the forerunner of the optical part of CANOPUS. There have been many extremely fruitful and interesting activities in the twenty years since I left Saskatoon in 1968. Suffice it to say that in collaboration with Dick Gattinger, the exploration of the auroral spectrum accessible from the ground was largely completed. Participation in the VIKING UV imager and the CANOPUS projects has been an exciting introduction to the new world of team-based "big" science. With these activities, there has been a continuity of working with my colleagues in the DASP community. It has been a pleasure and a privilege to work with so many fine people in all these enterprises.Link back to workshop transcript (AVJ on spectroscopy at UofS)
The material in this text is abstracted from a contribution to a paper planned in 1983 for the IAGA group on the History of Geophysics. To the best of my knowledge, other sections of the projected joint paper, covering work outside Canada, were never completed and the joint project was abandoned. A draft version of the present text was circulated to several interested people. The present version has been edited to emphasize the earlier developments in work on this field in Canada. This account is mostly about early Canadian studies of the spectrum of aurora carried out in the 1950-1965 period.
The first spectroscopic studies related to aurora carried out in Canada appear to have been those of Professor J.C. McLennan of the University of Toronto who was primarily interested in the 5577A green line and its origin. McLennan and Ireton (1930) obtained spectra from Caledon, Ontario and Sulphur Mountain, Alberta, and these show the 5577A line and also N2+ IN bands. McLennan and Schrum (1925) were the first to produce the 5577A line in the laboratory by means of a discharge with oxygen in a He buffer. They used a prism spectrograph, while later McLennan and McLeod (1927) repeated the measurement with a Fabry-Perot etalon to establish the wavelength at 5577.341+-.004. This agreed with the accurate value obtained by Babcock (1923) from the night sky and also enabled the green line to be assigned to the forbidden transition between the ground state configuration multiplets. The next significant activity occurred in connection with the Second International Polar Year, when a party was stationed at Chesterfield on the west side of northern Hudson Bay (63 201N, 900421W) (Currie, 1947). Professor B.W. Currie and F.T. Davies, then young staff members on leave from the University of Saskatchewan, obtained spectra on nearly all nights between December 1932 and April 1933 in August 1933. This work was done in very difficult conditions, more like those faced by polar explorers than those encountered by contemporary observers. The spectrograph used was the same as that employed by McLennan and Ireton. It was a glass prism instrument with an f/l lens recording the spectra on Ilford panchromatic plates (20 spectra to a plate). The analysis of these spectra was reported by Currie and Edwards (1936). A set of the spectrograms obtained is shown in Figure 1. Like all prism spectra these show the blue and UV bands of N2 and N2+ quite well with the green line strong near the long wavelength limit of the exposures. In their paper Currie and Edwards pioneered the use of spectrograms in compiling statistics of auroral occurrence and showed a good correlation with magnetic and earth current activity in the diurnal variation.
A new period of spectroscopic studies of aurora began at the University of Saskatchewan with the work of Professor W. Petrie who became interested in the subject of the atomic lines of 0 and N about 1947. He constructed a spectrograph with an f/2.5 camera lens and a 4"x4" 600 l/mm grating (Petrie, 1949). This instrument which was set with spectral slit widths of 5 to 20A, was used to photograph spectra in the photographic region from 3805A to the long wavelength limit of N plates. The infrared spectra were among the first to be obtained of this region. However the performance of the transmission lens optics was not sufficiently high to enable detailed spectra to be obtained with reasonably short exposures. Petrie's work excited interest and Nate Gerson of the U.S. Air Force Cambridge Research Laboratories and Petrie were offered a contract to perform basic research in aurora and airglow. This support was provided at about the same time that another contract arranged by Dr. Gerson provided generous support for the studies of radio aurora at Saskatchewan. This support, both financial and through provision of state of the art instrumentation, was most important in the aeronmy research program for the next 15 years. Through this connection was obtained the f/0.8 flat-field Schmidt camera which had just been developed by A.B. Meinel of Yerkes Observatory and used in pioneering studies of the infrared auroral and airglow spectrum. This camera was incorporated into a new 4"x5" grating spectrograph constructed at the University of Saskatchewan as shown in Figure 2. With this instrument, excellent spectra of aurora were obtained throughout the photographic spectral region from the UV cut-off at 3150A to the limit of sensitivity of N plates near 8900A. These spectra were published by Petrie and Small (1952a) and constitute an excellent atlas of the spectrum at a resolution of 2 to 5A. Petrie and Small discussed the features of the spectra in detail and particularly the allowed atomic lines in this paper and subsequently (Petrie and Small, 1953).
During the winter of 1950/1951 Petrie and Small (1952b) succeeded in getting very good UV spectra in the 3100 to 4750A range with a single prism quartz spectrograph which was constructed at the University of Saskatchewan by Dr. Gerhard Herzberg. The key components of this instrument were brought to Saskatoon from Germany by Dr. Herzberg in 1935. There is little doubt that the interest in spectroscopy implanted at Saskatchewan during Herzberg's time with the Physics Department paved the way for the work on auroral spectra which took place in the following decade.
Petrie left Saskatoon in 1952 to join the Radio Physics Laboratory of the Defence Research Board of Canada. However he left behind two research associates, Donald M. Hunten and myself who had joined him to work on the AFCRL contract. Hunten saw the possibilities of using photomultiplier tubes as detectors in conjunction with a grating monochromator provided with a wavelength scanning mechanism. The first instrument of this type (Dahlstrom and Hunten, 1951) was in fact improvised using a two-prism Littrow monochromator of which the Littrow mirror was rotated by a synchronous motor by means of an improvised string capstan. This arrangement was utilized on an expedition to Lac Laronge, Saskatchewan organized by Petrie. In a bright type-B red aurora this system obtained clear spectra showing the presence of the 02+ bands in the 5000 to 6000A region as well as to the detection of strong H-beta emission in a display of proton aurora seen to the south from Saskatoon. With the prisms replaced by a 4"x5" diffraction grating and the scanning achieved by a cam and lever arrangement, this design led to the realization of an extremely powerful instrument for auroral spectroscopy with the ability to obtain medium resolution spectra of aurora in about 15 secs or to study shorter wavelength ranges at higher resolution. This instrument (Hunten, 1953) was extensively used and improved by Hunten and his students between 1951 and 1963. Some of the earlier auroral results are given by Hunten (1955). Among the improvements made to the instrument were the extension of the wavelength range by means of cooled red sensitive PM tubes, the use of various memory systems to permit the averaging of spectra to improve the signal-to-noise ratio. Dry-ice refrigeration for the original blue sensitive tubes was replaced by mechanical refrigeration cooling, leading to the possibility of obtaining spectra at short notice when special displays occurred. It is hardly possible to summarize all the studies carried out by Hunten with this instrument; some of the most notable researches involved the measurement of upper atmospheric temperatures in aurora from the rotational structure of the N2+ bands (Hunten, 1961) and the observations of these bands in sunlit aurora (Lytle and Hunten, 1962). Dr. G.G. Shepherd did pioneering studies with Hunten at Saskatchewan on N2+ rotational temperatures with the scanning spectrometer. The same instrument was used by Broadfoot and Hunten (1964,1966) in important quantitative work on N2 and N2+ bands in aurora.
Petrie suggested to me when I arrived at Saskatchewan in 1952 that it might be of interest to try and explore the IR auroral spectrum beyond the photographic region. This study was attempted by building a scanning monochromator with a photoconductive PbS detector. Success with this system (at a spectral slit width of 200A) was achieved by Vallance Jones and Gush (1953) for both nightglow and aurora. It required several more years before definitive results were obtained on aurora as reported by Harrison and Vallance Jones (1959) and Shemansky (1960). These studies are summarized by Vallance Jones (1964).
The Meinel f/0.8 spectrograph built at Saskatoon by Petrie was operated by myself and my students during the next 15 years. The original Meinel camera was replaced by a new one with a fused quartz corrector and a second large spectrograph with an 8"x 8" grating built under Meinel's direction at Williams Bay was furnished through the U.S.A.F contract and was in operation in early 1953 with an f/2.5 camera. With this camera, this spectrograph gave for the first time, fully resolved spectra of the 3914A N2+ bands in aurora (Vallance Jones et al., 1953) but was not fast enough in practice to record other bands of the spectrum.
In 1955 an f/0.8 camera was made available for this spectrograph and it became possible to record the whole photographic auroral spectrum at higher dispersion than before. The instrument produced good results. An atlas of spectra produced by this instrument, the so-called 9" spectrograph, was presented by Vallance Jones (1965) (see, also, Omholt, 1971). Among the more notable results were the plates obtained of sunlit auroral rays demonstrating the Swings effect (Vallance Jones and Hunten, 1960) and the spectrum obtained during the Type-A red aurora of February 10-11, 1958 (Vallance Jones, 1960). After his arrival at the Radio Physics Laboratory in Ottawa, Petrie proceeded to obtain several spectrographs of the 5" and 9" Meinel type for a program of auroral spectroscopy based on Ft. Churchill. One of the 5" spectrographs was installed in a room at the top of a tower at Resolute Bay. After Petrie's connection with this program ended the work was carried on by R. Montalbetti and D.J. McEwen.
Another distinct continuing investigation engaged the interest of a number of Canadian spectroscopists. This was the attempt to use spectroscopic techniques to understand the appearance of the Balmer lines in the spectra of aurora. The work of Vegard, Meinel and Chamberlain had clearly established that the appearance of these lines indicated the presence of protons among the incident particles responsible for the excitation of aurora. It was also clear that most bright aurora is excited by electrons and consesquently to a reasonable approximation the incoming fluxes of protons and electrons can be estimated from spectra. This was recognized by Petrie and Small (1952a). From the beginning there was considerable interest in these studies because even the earliest auroral theories predicted that there should be certain differences in the latitude distribution of protons and electrons as a function of local time. An early attempt to define these effects in Canada was made by Montalbetti and Vallance Jones (1957) in which simultaneous spectrograms from Churchill and Saskatoon were compared.
No history of auroral spectroscopy in Canada would be complete without including the contribution of Professor R.W. Nicholls who, over three decades, has devoted a great deal of effort to providing observationists with theoretical and laboratory data essential to the quantitative interpretation of auroral spectra. In particular the Franck-Condon factors and band strengths compiled by Nicholls and his associates have been invaluable to all auroral spectroscopists. Professor Nicholls began this work at the University of Western Ontario and in 1965 moved to York Universtiy where he is the Director of the Centre for Research in Experimental Space Science.REFERENCES
*Babcock, H.D., A study of the green auroral line by the interference method, Astrophys. J., 57, 209, 1923.
*Broadfoot, A. L. and Hunten, D. M. 1964. Excitation of N2 band systems in aurora. Can. J. Phys. 42, 1212-1230.
*Broadfoot, A. L. and Hunten, D. M. 1966. N2+ emission in twilight. Planet. Space Sci. 14, 1303-1319.
**Currie, B.W., The polar aurora, J. Roy. Astron. Soc. Can., 41, 249, 1947.
*Currie, B.W., and H.W. Edwards, On the auroral spectrograms taken at Chesterfield, Canada during 1932-33, Terr. Magnet. and Atmos. Elect., 41, 264, 1936.
*Dahlstrom, C.E., and D.M. Hunten, 0; and H in the auroral spectrum, Phys. Rev., 84, 378, 1951.
*Harrison, A..W. and A. Vallance Jones. Observations of Meinel N2+ bands near 1.5 microns in the auroral spectrum. J. Atmos. Terr. Phys.. 13, 291. 1959.
*Hunten, D.M., A rapid-scanning auroral spectrometer, Can. J. Phys., 31, 681, 1953.
*Hunten, D.M., Some photomric observations of auroral spectra, J. Atmos. Terr. Phys., 7, 141, 1955.
*Hunten, D.M., Temperatures deduced from aurora and airglow spectra, Ann. Geophys. 17, 249, 1961.
*Lytle, E.A., and D.M. Hunten, Observations of N~ twilight and sunlit aurora, Can. J. Phys., 40, 1370, 1962.
*McLennan, J.C., and H.J.C. Ireton, Spectroscopy of the light from the night sky, Can. J. Res., 2, 279, 1930.
*McLennan, J.C., and J.H. McLeod, On the wavelength of the green auroral line in the oxygen spectrum, Proc. Roy. Soc., London, A115, 515, 1927.
*McLennan, J.C., and G.M. Shrum, On the origin of the auroral green line 5577 ~ and other spectra associated with aurora borealis, Proc. Roy. Soc., London, A108, 501, 1925.
*Montalbetti, R., and A. Vallance Jones, H-alpha emissions during aurorae over west-central Canada, J. Atmos. Terr. Phys., 11, 43, 1957.
*Omholt, A., The optical aurora, Springer-Verlag, Heidelberg, Germany, 1971,
*Petrie, W., A new high light gathering power spectrograph for auroral studies, Can. J. Res., A27, 231, 1949.
*Petrie, W., and R. Small, The auroral spectrum in the wavelength range 3300-8900 R, Astrophys. J., 116, 433, 1952a.
*Petrie, W., and R. Small, Auroral spectrum: Intensities of U.V. features, J. Geophys. Res., 57, 51, 1952b.
*Petrie, W., and R. Small, The intensities of atomic and molecular features in the auroral spectrum, Can. J. Phys., 31, 911,1953.
*Shemansky, D.E., A study of higher resolution spectra of the airglow and aurora from 1.4 micron to 1.65 micron, M.Sc. thesis, Univ. of Sask., Saskatoon, 1960.
*ValIance Jones, A., An Analysis of a spectrogram of the red aurora of February 10/11, 1958, in the wavelength range 7300-8700 A, Can. J. Phys., 38, 453, 1960.
*ValIance Jones, A., The telluric emission spectrum in the range 1 micron to 3 micron, Mem. Roy.Soc. Liege , 1964
*ValIance Jones, A., Optical measurements of auroras, Auroral Phenomena, Experiments and Theory, edited by M. Walt, Stanford Univ. Press, p. 20. 1965.
*ValIance Jones, A., and H. Gush, Spectrum of the night sky in the range 1.2- 2 microns, Nature l72, 496, 1953.Link back to workshop transcript (AVJ on spectroscopy at UofS)