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Recent eclipse work in Japan
Recent Eclipse Work in Japan Y U S U K E HAGIHARA Tokyo Astronomical Observatory, J a p a n SUMMARY
Eclipse work is summarized for the total eclipses on 1936 June 19, 1941 September 21, 1943 February 4-5, and for the am, ular eclipse on 1948 May 9--in which photographic and three-colour photoelectric photometry, spcctrophotometry, and polarization of the solar corona were studied. The solar limbdarkening was also investigated. In the geodetic programme during the annular eclipse for determining the figure and the dimension of the Earth the large plumb-line deviation of the Japanese Islands was confirmed.
SIS~CE 1934 Japan has been fortunate in having had several occasions for observing solar eclipses in her own islands. In 1936 Professor F. J. M. STRATTON and his collaborators came to Japan to observe the total solar eclipse at Kamishari in Hokkaido ; see Fig. 1 (a), (b), (c), (d). This event stimulated the study of eclipses in Japan, and several important papers have since been published. I . TOTAL SOLAR ECLIPSE OF 1936 J U N E
19 IST HOKKAIDO
MATUKUMA (1940) obtained, at Koshimizu, one EINSTEIN plate with a horizontal camera of aperature 20 cm, focal length 500 cm, and an exposure time of 80 sec. About ten stars were found on the plate, and from them, using two comparison plates of the same field taken at Sendai six months later, he derived an Einstein light deflection of 2':134 ! 1':146 and 1':284 4- 2':672, respectively. HAGIHARA and SAITO (1938) photographed, at Mombetsu, the solar corona with a Dallmeyer camera of 8 cm aperture. A special apparatus was devised for obtaining the intensity calibration of the coronal light, consisting of a cylindrical lens and an optical wedge. The photometric treatment of the plates was carried out with special care. The effect of halation on the photographic plates was studied with auxiliary laboratory experiments, and the effect of sky scattering with auxiliary observations. Both these effects were eliminated by solving FREDHOLM'S integral equations (HAGItIARA and SAITO, 1938; HAGIItARA, 1938). The effect of flare was studied by SAITO (1939) by using a similar method, and was shown to be negligible. After the completion of these discussions, the intensity distribution in space of the corona was derived by solving ABEL'S integral equation. From the plates, showing the intensity distribution of the light over the Moon's disc, the albedo of the Earth was derived. KABURAKI (1938) photographed, at Mombetsu, the inner corona through a yellow filter with a Merz visual equatorial of aperture 16-2 cm. He also obtained flash spectra with an objective prism and a Cook lens of aperture 18 cm. KUBOKAWA took photographs of several phases of the eclipse using a horizontal camera of focal length 11 m. HASIMOTO and OKUDA, at Naka-Tombetsu, obtained spectrograms of the corona with a Zeiss three-prism slit spectrograph, and SOTOME at Memambetsu tried to obtain an Einstein plate with a Cook triplet of aperture 30 cm. 7O8
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SEKIGUTI (1938) and KOlWAI, at Memambetsu-Nisshin, secured slitless spectrograms of the corona with an objective four-prism camera of focal length 25 cm, and found (SnKIGUTI, 1937) new emission lines at 6583"8 A and 6548.7 A, i.e. nearly coincident with the nebular lines 6583.6 A and 6548.1 A of [N II]. SEKIOUTI also found six new coronal lines with a two-prism slit spectrograph. These lines, however, have not yet been confirmed. TANAKA(TANAKA,KOANA, and KO~DO, 1945 ; TANAKA, OURA, and MURAKAMI, 1945), with the assistance of HATTORI, took slit spectra of the corona with a Littrow-type three-prism spectrograph at Shari, and obtained the wavelengths of the emission lines and the radial intensity decrement from the limb. NOTUKI, at Memambetsu-Nisshin, tried to get flash- and corona-spectra in the longer-wavelength regions with a slitless spectrograph and a plane grating, and FUJITA attempted similar observations in the shorter-wavelength regions with a Hilger quartz spectrograph. OIKAWA,at Kunneppu, also tried to get slitless flash spectra with a Steinheil 45 ° prism and a Cook 8?5 prism. The weather was not favourable for these observers. YAMAZAKI and GOTO (1937) succeeded in taking cinematograph films of the flash spectra, with time-marks, showing the transition from Fraunhofer lines to emission. Other parties tried to get Einstein plates and corona plates, but were not successful. Several parties went to Manchuria and to Siberia to take direct photographs of the corona, in order to study the changes of its shape during the eclipse in conjunction with the photographs taken with similar equipment at the three above-mentioned stations in Hokkaido. The result has not been published. I I . TOTAL SOLAR ECLIPSE ON 1941 SEPTEMBER 21 IN OKINAWA ISLANDS
OSAWA (1943) made a three-colour photometry of the corona with a simple photo electric photometer. The brightness of the corona in red, green, and violet light, respectively, was 0.27, 0.205, and 0.21, expressed in units of the full moon. He also observed the intensity distribution at the solar limb, using a Steinheil spectrograph and a photo-electric photometer. The output current of the amplifier was recorded cinematographically. He found that the darkening at the extreme limb was much steeper than one would have expected from the well-known law of the intensity distribution over the central zone of the solar disc. SEKmUTI observed the flash- and the corona-spectra by means of a miniature spectrograph of his own design, using glass prisms and a hyperboloid camera mirror. The observation was successful, but no new features were discovered. OIKAWA and SAITO took a corona spectrum with a three-prism spectrograph, consisting of Jobin's prisms, a Zeiss collimator lens of focal length 91 cm, and a Steinheil camera-lens of focal length 54 cm. The dispersion was 55.7 A per mm at ~6374, and 8.7 A per mm at 24231. Only one exposure of 180 sec. was made, with the slit tangential to the solar limb. An iron arc at reduced pressure was recorded on the plate. The wavelengths of the coronal lines were measured with great care, giving ,~6374.057 A, 5303.010 A, 5116.014 A, 4566.412 ~, 4231,135 A. FUJITA made spectrophotometric observations of the corona with a slitless spectrograph. It had five dispersing prisms and two right-angle reflecting prisms. The camera lens had an aperture of 2.3 cm, and a focal length of 58 cm. The dispersion was 7.0 A per mm at ~4800. Comparing the coronal light with a standard lamp and with photospheric light, FUJITA (1943, 1944) derived the absolute value of
YUSUKE HAGIHARA
71
the intensity of 45303, the electron pressure in the prominence, the density gradient of hydrogen atoms, and the profile of the Moon's limb, The above observations were made at Ishigaki Island in the Okinawa Island group. TANAKA went to Paichou, China, to observe corona spectra with a large slit spectrograph, mounted equatorially. M A T U K U M A , at the same place, tried to get flash- and corona-plates. UETA tried to obtain an Einstein plate at H~sh~ngchiao, Central China. The weather, however, was unfavourable, both at Paichou and at H~sh~ngchiao. III.
TOTAL
SOLAR ECLIPSE
ON
1943
FEBRUARY
4--5 IN H O K K A I D O
SAITO (1948) observed photographically the polarization of the corona, using an equatorial polarigraph with a Rochon prism, and a red filter of effective wavelength 0.6S/t. By measuring the double images of the corona, photographed at various position angles of the Rochon prism, he determined the degree of polarization and the plane of polarization in different parts of the corona. The direction of the polarization was shown to be almost radial to the solar limb, not deviating by more than 10 °. The polar polarization exceeded the equatorial polarization near the limb, but the two became nearly equal at 4' from the limb. The situation was seen to be reversed in the outer corona. SAITO (1950) then proposed an interpretation of this result, based on a theory in which the oblateness of the corona was taken into account. HURU]{ATA (1947), on the other hand, measured the polarization of the corona photo-electrically with a 13 cm Cook refractor of focal length 168.4 cm, colour filters, a Nicol prism, a vacuum potassium phototube, a high resistance in vacuo, and a UX 54 tube. The amplified photocurrent was recorded automatically by means of a sliding-plate equipment. The polarization was measured at five points of the corona along a radial direction from the Sun's centre, assuming the plane of polarization to be radial. Care was taken to eliminate the sky light. The results of SAITO and of HURUnATA arc in agreement. OSAWA observed the brightness distribution at the extreme limb of the Sun by means of three-colour photoelectric photometry, but the result was unsatisfactory, owing to the low altitude of the Sun. FUJITA (1949) observed the brightness distribution at the solar limb by SCHWARZSCHILD'S method, using a slitless spectrograph with a rocking-plate camera. Twenty exposures, each of 0.01 sec., were made at intervals of 5 sec. FUJITA solved the well-known integral equations of the problem, and concluded that the brightness distribution was approximately represented by a linear relationship with respect to cos 0 (for 45200, 45300, or 45400); the brightness was lower than the value given by the linear relation for 0.28 > cos 0 > 0.18, and higher for 0.18 ~ cos 0 > 0.13. •OTUKI took flash- and corona-spectrograms, mainly with the intention of measuring the relative strengths of the green and the red coronal lines. The above observations were made at Akkeshi, Hokkaido. T A N A K A , O U R A , M A T U K U M A , and MITUNOBU (1946) observed the coronal spectrum at Yubetsu, Hokkaido. They determined accurate wavelengths of coronal lines, including the new line 45306.40 which TANAKA observed at the eclipse of 1936. The brightness distribution and the polarization of the corona were also studied by * This eclipse began on 1943 February 4 at 21h 26m G.M.T., and ended oil February 5 at 01h 49m.
712
Recent eclipse work in J a p a n
putting a Wollaston quartz-prism behind the collimator lens. The maximum polarization occurred at a distance of about one-half solar radius from the limb. MATUKUMA obtained at Kushiro a spectrogram of the corona with a three-prism slit spectrograph; he noticed some unknown lines. IV.
A N N U L A R E C L I P S E S ON 1 9 4 8
M A Y 9 AT R E B U N
ISLAND IN H O K K A I D O
An Eclipse Committee was organized by the National Research Council, consisting of astronomers, geophysicists, and ionosphere workers. As well as organizing our own observational programme (Nat. Res. Coun. Japan, 1948), the Committee also worked in co-operation with the American National Geographic Society on their geodetic programme. HIROSE (1948) found, from previous observations of occultations, the systematic deviation of the observations in Japan from those made in Europe and America. He attributed it to the systematic deviation of the vertical in the Japanese islands, due to the presence of the big Asiatic continent to the West, and of the deep Pacific oceanic basin to the East. The amount of this deviation could explain the systematic discrepancy found by the land survey along the boundary of Manchuria and Korea. Thus, the results of these eclipse observations confirmed HIROSE'S theory. KAHO (1949) took direct photographs of the partial phases with a horizontal camera, the objective lens of which had an aperture of 18 cm and a focal length of 500 cm. Sixty-two plates were obtained, and the relative position of Sun and Moon computed ( H I R o S E , K A H O , a n d TOMITA, 1950). O S A W A (1951) observed the brightness distribution at the extreme limb of the Sun using JULIUS' method. A photo-electric photometer with a potassium vacuumphototube served for recording the variation of the integrated brightness of an effective wavelength of about 24000. The analysis of the results, solving the wellknown integral equation, showed that the intensity dropped rapidly at the extreme limb. UETA and FUJINAMI photographed the partial and the annular phases. FUJINAMI (1952), with the collaboration of a group of cinematograph technicians, obtained cine films of Bailey's beads. He recorded the heights of the mountains and the depths of the valleys on the lunar surface; the depths of some of the valleys were found to be much deeper than previously determined by HAYN.
REFERENCES FUJITA, Y .
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FUJINAMI, S . . . . . . . . . . . . GOTO, S. a n d YAMASAKI, M . . . . . . . . HAGIHARA, Y . . . . . . . . . . . . HAGIHARA, ~'. and SAITO, K . . . . . . . HIROSE, H .
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HIROSE, H., KAHO, S. HURUHATA, M . . . KABURA~:I, M . . . KAHO, S . . . . . MATUKUMA, W. . .
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and TOMITA, K . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1943 1944 1949 1952 1937 1938 1938 1938 1948 1948 1950 1947 1938 1949 1940 1940
Japan J. Astron. Geophys., 20, 83. Ibid., 21, 1. Publ. Astron. Soc. Japan, 1, 23. Publ. Astron. Soc. Japan, 4, 115. Popul. Astron., 45, No. 5. Astron. Nachr., 266, 285. Ann. Tokyo Astron. Obs., Ser. I I , 1, 91. Ibid., 151. Proc. Japan Acad., 24, 35, 51, 56. Tokyo Astron. Obs. Repr., Nos. 83, 84, 85. Ann. Tokyo Astrvn. Obs., Ser. I I , 3, 23. Japan J. Astron. Geophys., 21, 173. Ann. Tokyo Astron. Obs., Ser. I I , 1, 139. Tokyo Astron. Obs. Repr., No. 39. Japan J. Astron. Geophys., 18, 51. Nature (London), 146, 264.
713
R. O. REDMAN OSAWA, K .
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1943 1943
Tokyo Astron. Bull., Nos. 692-695. Tokyo Astron. Obs. Rep., 9, 143 (in
1951 1948 1939 1948 1950 1937 1938 1945 1945
Ann. Tokyo Astron. Obs., Ser. I I , 3, 53. Solar Eclipse Committee: Provisional Report of Observations of the Annular Eclipse on 9th May, 1948. Ann. Tokyo Astron. Obs., Ser. I I , 1, 201. Tokyo Astron. Bull., Ser. I I , No. 8. Ann. Tokyo Astron. Obs., Ser. I I , 3, 1. Nature (London), 140, 724. Ann. Tokyo Astron. Obs., Ser. I I , 1~ 59. J. Phys. Soc. Japan, 1, 31. ibid., 30.
1946
J. Phys. Soc. Japan, 1, 30.
Japanese). Nat. Res. Coun. J a p a n , Tokyo
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SAITO, K .
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SEKIGUTI, R .
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TANAKA, T., KOANA, Z. a n d KONDO, K.
TANAKA, T., OURA, H. a n d MURAKAMI, T.
. . TANAKA, T., OURA, H., MATUKUMA, T. a n d MITUNOBU, T . . . . . . . . . . .
The Widths of Narrow Lines in the Spectrum of the Low Chromosphere, Measured at the Total Eclipse of February 25, 1952. R. O. REDMAN The Observatories, Cambridge
SUMMARY The s p e c t r u m of the c h r o m o s p h e r e was p h o t o g r a p h e d at the total solar eclipse of 25th F e b r u a r y , 1952, with a slit spectrograph, using the second order of a 6-in. R o w l a n d concave grating. Line w i d t h s were m e a s u r e d in b o t h ultra-violet a n d yellow. B o t h regions show ~0 near 2.5 k m per sec. for h e a v y elements in the lowest c h r o m o s p h e r e (average line of sight velocity a b o u t 1.8 k m per sec.), in close agreement with m e a s u r e s m a d e at the 1940 eclipse. There is some evidence for a small increase of velocity with height.
1. I N T R O D U C T I O N
THE question of the distribution of material velocities within the chromosphere, whether of the nature of turbulence in an essentially dynamic atmosphere, or of a temperature in an approximately static medium, is of fundamental importance to all theories of the structure of this part of the Sun's atmosphere. Perhaps the best way of obtaining evidence on this point is to measure accurately the shapes of lines in the chromospheric spectrum. The method is not free from serious difficulties, but at least it can give an upper limit to the velocity spread at any particular chromospheric level. It can also distinguish to some extent between turbulent motion, where the velocities are the same for all constituents of the gas, and thermal motions where the velocities vary with atomic weight. The chief difficulty is that there are other mechanisms of line broadening, the most important being self-absorption, so that to obtain significant velocity data the lines for measurement have to be selected with great care. In good seeing and in longer wavelengths, say 2 ~ 5000 A, the chromospheric spectrum has been photographed in broad daylight, first by HALE, and later by ADAMS and others. Dr. H. D. BABCOCK, who is among those who have made use of this procedure, has recently drawn attention to the possibility of measuring the shapes of the chromospheric lines in this way (BABCOCK, 1954). However, up till now observers have chosen to measure line widths at eclipses, the inconvenience of an
Eclipse work is summarized for the total eclipses on 1936 June 19, 1941 September 21, 1943 February 4-5, and for the am, ular eclipse on 1948 May 9--in which photographic and three-colour photoelectric photometry, spcctrophotometry, and polarization of the solar corona were studied. The solar limbdarkening was also investigated. In the geodetic programme during the annular eclipse for determining the figure and the dimension of the Earth the large plumb-line deviation of the Japanese Islands was confirmed.
SIS~CE 1934 Japan has been fortunate in having had several occasions for observing solar eclipses in her own islands. In 1936 Professor F. J. M. STRATTON and his collaborators came to Japan to observe the total solar eclipse at Kamishari in Hokkaido ; see Fig. 1 (a), (b), (c), (d). This event stimulated the study of eclipses in Japan, and several important papers have since been published. I . TOTAL SOLAR ECLIPSE OF 1936 J U N E
19 IST HOKKAIDO
MATUKUMA (1940) obtained, at Koshimizu, one EINSTEIN plate with a horizontal camera of aperature 20 cm, focal length 500 cm, and an exposure time of 80 sec. About ten stars were found on the plate, and from them, using two comparison plates of the same field taken at Sendai six months later, he derived an Einstein light deflection of 2':134 ! 1':146 and 1':284 4- 2':672, respectively. HAGIHARA and SAITO (1938) photographed, at Mombetsu, the solar corona with a Dallmeyer camera of 8 cm aperture. A special apparatus was devised for obtaining the intensity calibration of the coronal light, consisting of a cylindrical lens and an optical wedge. The photometric treatment of the plates was carried out with special care. The effect of halation on the photographic plates was studied with auxiliary laboratory experiments, and the effect of sky scattering with auxiliary observations. Both these effects were eliminated by solving FREDHOLM'S integral equations (HAGItIARA and SAITO, 1938; HAGIItARA, 1938). The effect of flare was studied by SAITO (1939) by using a similar method, and was shown to be negligible. After the completion of these discussions, the intensity distribution in space of the corona was derived by solving ABEL'S integral equation. From the plates, showing the intensity distribution of the light over the Moon's disc, the albedo of the Earth was derived. KABURAKI (1938) photographed, at Mombetsu, the inner corona through a yellow filter with a Merz visual equatorial of aperture 16-2 cm. He also obtained flash spectra with an objective prism and a Cook lens of aperture 18 cm. KUBOKAWA took photographs of several phases of the eclipse using a horizontal camera of focal length 11 m. HASIMOTO and OKUDA, at Naka-Tombetsu, obtained spectrograms of the corona with a Zeiss three-prism slit spectrograph, and SOTOME at Memambetsu tried to obtain an Einstein plate with a Cook triplet of aperture 30 cm. 7O8
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©
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710
Recent eclipse work in Japan
SEKIGUTI (1938) and KOlWAI, at Memambetsu-Nisshin, secured slitless spectrograms of the corona with an objective four-prism camera of focal length 25 cm, and found (SnKIGUTI, 1937) new emission lines at 6583"8 A and 6548.7 A, i.e. nearly coincident with the nebular lines 6583.6 A and 6548.1 A of [N II]. SEKIOUTI also found six new coronal lines with a two-prism slit spectrograph. These lines, however, have not yet been confirmed. TANAKA(TANAKA,KOANA, and KO~DO, 1945 ; TANAKA, OURA, and MURAKAMI, 1945), with the assistance of HATTORI, took slit spectra of the corona with a Littrow-type three-prism spectrograph at Shari, and obtained the wavelengths of the emission lines and the radial intensity decrement from the limb. NOTUKI, at Memambetsu-Nisshin, tried to get flash- and corona-spectra in the longer-wavelength regions with a slitless spectrograph and a plane grating, and FUJITA attempted similar observations in the shorter-wavelength regions with a Hilger quartz spectrograph. OIKAWA,at Kunneppu, also tried to get slitless flash spectra with a Steinheil 45 ° prism and a Cook 8?5 prism. The weather was not favourable for these observers. YAMAZAKI and GOTO (1937) succeeded in taking cinematograph films of the flash spectra, with time-marks, showing the transition from Fraunhofer lines to emission. Other parties tried to get Einstein plates and corona plates, but were not successful. Several parties went to Manchuria and to Siberia to take direct photographs of the corona, in order to study the changes of its shape during the eclipse in conjunction with the photographs taken with similar equipment at the three above-mentioned stations in Hokkaido. The result has not been published. I I . TOTAL SOLAR ECLIPSE ON 1941 SEPTEMBER 21 IN OKINAWA ISLANDS
OSAWA (1943) made a three-colour photometry of the corona with a simple photo electric photometer. The brightness of the corona in red, green, and violet light, respectively, was 0.27, 0.205, and 0.21, expressed in units of the full moon. He also observed the intensity distribution at the solar limb, using a Steinheil spectrograph and a photo-electric photometer. The output current of the amplifier was recorded cinematographically. He found that the darkening at the extreme limb was much steeper than one would have expected from the well-known law of the intensity distribution over the central zone of the solar disc. SEKmUTI observed the flash- and the corona-spectra by means of a miniature spectrograph of his own design, using glass prisms and a hyperboloid camera mirror. The observation was successful, but no new features were discovered. OIKAWA and SAITO took a corona spectrum with a three-prism spectrograph, consisting of Jobin's prisms, a Zeiss collimator lens of focal length 91 cm, and a Steinheil camera-lens of focal length 54 cm. The dispersion was 55.7 A per mm at ~6374, and 8.7 A per mm at 24231. Only one exposure of 180 sec. was made, with the slit tangential to the solar limb. An iron arc at reduced pressure was recorded on the plate. The wavelengths of the coronal lines were measured with great care, giving ,~6374.057 A, 5303.010 A, 5116.014 A, 4566.412 ~, 4231,135 A. FUJITA made spectrophotometric observations of the corona with a slitless spectrograph. It had five dispersing prisms and two right-angle reflecting prisms. The camera lens had an aperture of 2.3 cm, and a focal length of 58 cm. The dispersion was 7.0 A per mm at ~4800. Comparing the coronal light with a standard lamp and with photospheric light, FUJITA (1943, 1944) derived the absolute value of
YUSUKE HAGIHARA
71
the intensity of 45303, the electron pressure in the prominence, the density gradient of hydrogen atoms, and the profile of the Moon's limb, The above observations were made at Ishigaki Island in the Okinawa Island group. TANAKA went to Paichou, China, to observe corona spectra with a large slit spectrograph, mounted equatorially. M A T U K U M A , at the same place, tried to get flash- and corona-plates. UETA tried to obtain an Einstein plate at H~sh~ngchiao, Central China. The weather, however, was unfavourable, both at Paichou and at H~sh~ngchiao. III.
TOTAL
SOLAR ECLIPSE
ON
1943
FEBRUARY
4--5 IN H O K K A I D O
SAITO (1948) observed photographically the polarization of the corona, using an equatorial polarigraph with a Rochon prism, and a red filter of effective wavelength 0.6S/t. By measuring the double images of the corona, photographed at various position angles of the Rochon prism, he determined the degree of polarization and the plane of polarization in different parts of the corona. The direction of the polarization was shown to be almost radial to the solar limb, not deviating by more than 10 °. The polar polarization exceeded the equatorial polarization near the limb, but the two became nearly equal at 4' from the limb. The situation was seen to be reversed in the outer corona. SAITO (1950) then proposed an interpretation of this result, based on a theory in which the oblateness of the corona was taken into account. HURU]{ATA (1947), on the other hand, measured the polarization of the corona photo-electrically with a 13 cm Cook refractor of focal length 168.4 cm, colour filters, a Nicol prism, a vacuum potassium phototube, a high resistance in vacuo, and a UX 54 tube. The amplified photocurrent was recorded automatically by means of a sliding-plate equipment. The polarization was measured at five points of the corona along a radial direction from the Sun's centre, assuming the plane of polarization to be radial. Care was taken to eliminate the sky light. The results of SAITO and of HURUnATA arc in agreement. OSAWA observed the brightness distribution at the extreme limb of the Sun by means of three-colour photoelectric photometry, but the result was unsatisfactory, owing to the low altitude of the Sun. FUJITA (1949) observed the brightness distribution at the solar limb by SCHWARZSCHILD'S method, using a slitless spectrograph with a rocking-plate camera. Twenty exposures, each of 0.01 sec., were made at intervals of 5 sec. FUJITA solved the well-known integral equations of the problem, and concluded that the brightness distribution was approximately represented by a linear relationship with respect to cos 0 (for 45200, 45300, or 45400); the brightness was lower than the value given by the linear relation for 0.28 > cos 0 > 0.18, and higher for 0.18 ~ cos 0 > 0.13. •OTUKI took flash- and corona-spectrograms, mainly with the intention of measuring the relative strengths of the green and the red coronal lines. The above observations were made at Akkeshi, Hokkaido. T A N A K A , O U R A , M A T U K U M A , and MITUNOBU (1946) observed the coronal spectrum at Yubetsu, Hokkaido. They determined accurate wavelengths of coronal lines, including the new line 45306.40 which TANAKA observed at the eclipse of 1936. The brightness distribution and the polarization of the corona were also studied by * This eclipse began on 1943 February 4 at 21h 26m G.M.T., and ended oil February 5 at 01h 49m.
712
Recent eclipse work in J a p a n
putting a Wollaston quartz-prism behind the collimator lens. The maximum polarization occurred at a distance of about one-half solar radius from the limb. MATUKUMA obtained at Kushiro a spectrogram of the corona with a three-prism slit spectrograph; he noticed some unknown lines. IV.
A N N U L A R E C L I P S E S ON 1 9 4 8
M A Y 9 AT R E B U N
ISLAND IN H O K K A I D O
An Eclipse Committee was organized by the National Research Council, consisting of astronomers, geophysicists, and ionosphere workers. As well as organizing our own observational programme (Nat. Res. Coun. Japan, 1948), the Committee also worked in co-operation with the American National Geographic Society on their geodetic programme. HIROSE (1948) found, from previous observations of occultations, the systematic deviation of the observations in Japan from those made in Europe and America. He attributed it to the systematic deviation of the vertical in the Japanese islands, due to the presence of the big Asiatic continent to the West, and of the deep Pacific oceanic basin to the East. The amount of this deviation could explain the systematic discrepancy found by the land survey along the boundary of Manchuria and Korea. Thus, the results of these eclipse observations confirmed HIROSE'S theory. KAHO (1949) took direct photographs of the partial phases with a horizontal camera, the objective lens of which had an aperture of 18 cm and a focal length of 500 cm. Sixty-two plates were obtained, and the relative position of Sun and Moon computed ( H I R o S E , K A H O , a n d TOMITA, 1950). O S A W A (1951) observed the brightness distribution at the extreme limb of the Sun using JULIUS' method. A photo-electric photometer with a potassium vacuumphototube served for recording the variation of the integrated brightness of an effective wavelength of about 24000. The analysis of the results, solving the wellknown integral equation, showed that the intensity dropped rapidly at the extreme limb. UETA and FUJINAMI photographed the partial and the annular phases. FUJINAMI (1952), with the collaboration of a group of cinematograph technicians, obtained cine films of Bailey's beads. He recorded the heights of the mountains and the depths of the valleys on the lunar surface; the depths of some of the valleys were found to be much deeper than previously determined by HAYN.
REFERENCES FUJITA, Y .
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FUJINAMI, S . . . . . . . . . . . . GOTO, S. a n d YAMASAKI, M . . . . . . . . HAGIHARA, Y . . . . . . . . . . . . HAGIHARA, ~'. and SAITO, K . . . . . . . HIROSE, H .
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HIROSE, H., KAHO, S. HURUHATA, M . . . KABURA~:I, M . . . KAHO, S . . . . . MATUKUMA, W. . .
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and TOMITA, K . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1943 1944 1949 1952 1937 1938 1938 1938 1948 1948 1950 1947 1938 1949 1940 1940
Japan J. Astron. Geophys., 20, 83. Ibid., 21, 1. Publ. Astron. Soc. Japan, 1, 23. Publ. Astron. Soc. Japan, 4, 115. Popul. Astron., 45, No. 5. Astron. Nachr., 266, 285. Ann. Tokyo Astron. Obs., Ser. I I , 1, 91. Ibid., 151. Proc. Japan Acad., 24, 35, 51, 56. Tokyo Astron. Obs. Repr., Nos. 83, 84, 85. Ann. Tokyo Astrvn. Obs., Ser. I I , 3, 23. Japan J. Astron. Geophys., 21, 173. Ann. Tokyo Astron. Obs., Ser. I I , 1, 139. Tokyo Astron. Obs. Repr., No. 39. Japan J. Astron. Geophys., 18, 51. Nature (London), 146, 264.
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Ann. Tokyo Astron. Obs., Ser. I I , 3, 53. Solar Eclipse Committee: Provisional Report of Observations of the Annular Eclipse on 9th May, 1948. Ann. Tokyo Astron. Obs., Ser. I I , 1, 201. Tokyo Astron. Bull., Ser. I I , No. 8. Ann. Tokyo Astron. Obs., Ser. I I , 3, 1. Nature (London), 140, 724. Ann. Tokyo Astron. Obs., Ser. I I , 1~ 59. J. Phys. Soc. Japan, 1, 31. ibid., 30.
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TANAKA, T., KOANA, Z. a n d KONDO, K.
TANAKA, T., OURA, H. a n d MURAKAMI, T.
. . TANAKA, T., OURA, H., MATUKUMA, T. a n d MITUNOBU, T . . . . . . . . . . .
The Widths of Narrow Lines in the Spectrum of the Low Chromosphere, Measured at the Total Eclipse of February 25, 1952. R. O. REDMAN The Observatories, Cambridge
SUMMARY The s p e c t r u m of the c h r o m o s p h e r e was p h o t o g r a p h e d at the total solar eclipse of 25th F e b r u a r y , 1952, with a slit spectrograph, using the second order of a 6-in. R o w l a n d concave grating. Line w i d t h s were m e a s u r e d in b o t h ultra-violet a n d yellow. B o t h regions show ~0 near 2.5 k m per sec. for h e a v y elements in the lowest c h r o m o s p h e r e (average line of sight velocity a b o u t 1.8 k m per sec.), in close agreement with m e a s u r e s m a d e at the 1940 eclipse. There is some evidence for a small increase of velocity with height.
1. I N T R O D U C T I O N
THE question of the distribution of material velocities within the chromosphere, whether of the nature of turbulence in an essentially dynamic atmosphere, or of a temperature in an approximately static medium, is of fundamental importance to all theories of the structure of this part of the Sun's atmosphere. Perhaps the best way of obtaining evidence on this point is to measure accurately the shapes of lines in the chromospheric spectrum. The method is not free from serious difficulties, but at least it can give an upper limit to the velocity spread at any particular chromospheric level. It can also distinguish to some extent between turbulent motion, where the velocities are the same for all constituents of the gas, and thermal motions where the velocities vary with atomic weight. The chief difficulty is that there are other mechanisms of line broadening, the most important being self-absorption, so that to obtain significant velocity data the lines for measurement have to be selected with great care. In good seeing and in longer wavelengths, say 2 ~ 5000 A, the chromospheric spectrum has been photographed in broad daylight, first by HALE, and later by ADAMS and others. Dr. H. D. BABCOCK, who is among those who have made use of this procedure, has recently drawn attention to the possibility of measuring the shapes of the chromospheric lines in this way (BABCOCK, 1954). However, up till now observers have chosen to measure line widths at eclipses, the inconvenience of an