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The correlation of radio source scintillation in the southern and northern hemispheres
Research notes which was used as a base, but it seems to us that this effect would be negligible because of such a similarity between s.i.s and s.c.s at all stations as seen in Fig. 2. Thus our results will be qualitatively accepted at least. We hope that more active studies will be made on s.i.s as well as S.C.S. Acknowledgements-The authors wish to express their appreciation of t’he Kakioka Magnetic Observatory, for .his helpful discussions, for her assistance in the numerical analysis of the data.
to Mr. Y. YAMAGUCHI, and to Miss Y. YOKOI H. MAEDA M. YAMAMOTO
Geophysical Institute Kyoto University Kyoto, Japan REFERENCES FERR_~RO V. C. A.,PARKINSON W.C. ~~~UNTHANKH.W. JACKSON 'c1;. MAEDAH.~~~YAMAMOTO M. YAMAGUCHIY.
1951 1952 1960 1958
J. Geophys. Res. 56, 177. J. Atmosph. Terr. Phys. 2, 160. J. Geophys. Res. 65, In press. Mem. Kakioka Magn. Observ. 8, 33.
The correlation of radio source scintillation in the southern and northern hemispheres (Received 30 August 1960)
MANY modern aurora1 theories are based on the motions of charged particles trapped in the magnetic field lines between the southern and northern aurora1 zones. According to some of these theories aurora1 and ionospheric disturbances occur when the captive particles are caused to spill out of their orbits into the atmosphere, and the disturbances should be detected simultaneously in each hemisphere (VAN ALLEN, 1959; VESTINE, 1959). In view of the fact that an aurora1 origin of radio source scintillation has been questioned (DAGG, 1957b) it is interesting to determine whether or not the scintillation activity in high southern latitudes is related to the activity in northern latitudes. Scintillation observations were made during the International Geophysical Year at the Royal Society Base, Halley Bay, Antarctica and have been compared with simultaneous observations made at Jodrell Bank in England. A full description of the methods and results of the Halley Bay observations have been given by BRENAN (1960) and the Jodrell Bank observations have been described by CHIVERS (1960) and earlier workers. The details of the programmes undertaken at the two stations are not important to the present discussion and need not be repeated here. It is necessary however to refer to the positions of the stations and their coordinates are listed in Table 1. It can be seen from this table that the mutual placing of the stations is not ideal for comparisons of the activity in the two hemispheres, although it is more nearly so than for any other pair of stations operating during the International Geophysical Year. This is because the longitude of Halley Bay is 24” west of Jodrell Bank and this corresponds to a phase difference in any possible diurnal variation of activity at the two places of nearly 2 hr. Neither are the stations ideally situated with respect to the geomagnetic field since it is at places at either end of a field line that especially high correlation might be expected (VESTINE, 1959). VESTINE has computed the conjugate points of a selected number of 287
Research notes Table
1.
Geographic coordinates
Station Halley Bay Jodrell Bank
75”31’S 1 “6”36’ I%53”14’ N 2”18’ W
Geomagnetic coordinates 65.8’ S 24.3” E 56.3” N 82.5’ E
stations using the observed magnetic field, and by interpolation of his results it transpires that the field line passing outwards at Halley Bay enters the ionosphere again in the vicinity of 54”N 22”W far to the west of Jodrell Bank. The Halley Bay scintillation observations used here are those of the Centaurus radio source made near the time of its upper culmination at Halley Bay. The data available at Jodrell Bank concerns the radio source in Cassiopeia which at that time bears approximately 3O”E of N of the station, and the line of
Jodrell Fig.
Bank
fluctuation
amplitude,
%
1. Correlation of scintillation amplitude at Jodrell Bank and Halley Bap (Nedian values and interquartile ranges).
sight to the source then passes through the ionosphere several hundred kilometres distant from Jodrell Bank at a point nearly 2000 km from the conjugate point of Halley Bay. The scintillation amplitude at Halley Bay at each upper culmination observation has been compared with the amplitude measured at the same time at Jodrell Bank. The correlation diagram is shown in the figure and the correlation coefficient is +0*37 for 388 pairs of observations. This is a statistically significant correlation. Moreover the correlation coefficient would probably have been higher still if it were not for the limitations that have been mentioned earlier. The physical significance of the correlation is less obvious and will be discussed next. Few results have been published on the day-to-day correlation of scintillation activity at stations separated by a few hundred kilometres, and they are restricted to places in the same hemisphere. Thus though LITTLE and LOVELL (1950), KOSTER (1958), STANLEY and SLEE (1950)and REID (1957) have all considered some aspects of the differences between the scintillation at distant stations only the first two publications refer to the question of whether scintillation can occur at one station without being detected at the other. 288
Research
notes
Using the data given by LITTLE and LOVELL for sixty-six observations of the Cassiopeia source it appears that the correlation coefficient relating the occurrence of scintillation at Cambridge and Jo&e11 Bank (210 km apart) was +O*SS. The correlation analysis made by KOSTER of the simultaneous occurrence of scintillation at Cambridge and Ghana showed that the activity was unrelated at the two places. The correlation coefficient between twenty-two pairs of observations was only $0.08. When these values are compared with the correlation coefficient + 0.37 derived from Halley Bag and Jodrell Bank data it appears that there is a closer connexion between the scintillation occurring at high latitudes in the two hemispheres than between that occurring at a high latitude and the equator. This suggests that there may be a distinction between the origin of equatorial and high latitude scintillation and the distinction is emphasized when the close correlation observed between high latitude scintillation activity and magnetic disturbances (DAGG, 1957a; CHIVERS,1960; BRENAN, 1960) is compared with the singular lack of correlation between equatorial scintillation activity and magnetic disturbances (KOSTER, 1958). It was the difficulty of explaining equatorial and high latitude scintillation together in a single theory that led DAGG (1957b) to reject the idea of an aurora1 origin of scintillation. The results quoted here however suggest that no single theory could be expected to account for both types of scintillation, and the demonstrated correlation between the activity at Halley Bay and Jo&e11 Bank strengthens the view that high latitude scintillation and aurora1 activity are closely associated. Acknowledgements-1 am grateful to Dr. H. J. A. CHIVERSfor providing the Joclrell Bank scintillation data. The work formed part of the programme of the British National Committee for the International Geophysical Year. P. M. BRENAN Xuffield Radio Astronomy Laboratories Jodrell Bank, University of Manchester REFERENCES BRENANP. M.
1960
CHIVERSH. J. A. DAGUM. DAGGM. KOSTERJ. R. LITTLEC. G. and LOVELLA. C. B. REID G. C. STANLEYG. J. and SLEE0. B. VAN hLEZr J. A. VESTINEE. H.
1960 1957a 195713 1958 1950 1957 1950 1959 1959
The Royal Society, I.G. Y. Antarctic Expedition, Halley Bay, Coates Land, Falkland Islands Dependencies, 1955-1959, Vol. 2. The Royal Society, London. In press. J. Atmosph. Terr. Phys. In press. J. Atmosph. Terr. Phys. 10, 194. J. Atmosph. Terr. Phys. 11, 133. J. Atmosph. Terr. Phys. 12, 100. Nature, Lond. 165, 423. Canad. J. Phys. 35, 1004. Au&. J. Phys. A 3, 234. J. Geophys. Res. 64, 1683. J. Geophys. Res. 64, 1411.
The magnetic storm-time variation of radio star scintillations and aurora1 radio echoes (ReceivedI September 1960) CONTINUOUS observations have been made at Jodrell Bank since the 1954 sunspot minimum, of radio star scintillations of the source in Cassiopeia and of radio echoes from the aurora
lo-(12pp.)
289
to Mr. Y. YAMAGUCHI, and to Miss Y. YOKOI H. MAEDA M. YAMAMOTO
Geophysical Institute Kyoto University Kyoto, Japan REFERENCES FERR_~RO V. C. A.,PARKINSON W.C. ~~~UNTHANKH.W. JACKSON 'c1;. MAEDAH.~~~YAMAMOTO M. YAMAGUCHIY.
1951 1952 1960 1958
J. Geophys. Res. 56, 177. J. Atmosph. Terr. Phys. 2, 160. J. Geophys. Res. 65, In press. Mem. Kakioka Magn. Observ. 8, 33.
The correlation of radio source scintillation in the southern and northern hemispheres (Received 30 August 1960)
MANY modern aurora1 theories are based on the motions of charged particles trapped in the magnetic field lines between the southern and northern aurora1 zones. According to some of these theories aurora1 and ionospheric disturbances occur when the captive particles are caused to spill out of their orbits into the atmosphere, and the disturbances should be detected simultaneously in each hemisphere (VAN ALLEN, 1959; VESTINE, 1959). In view of the fact that an aurora1 origin of radio source scintillation has been questioned (DAGG, 1957b) it is interesting to determine whether or not the scintillation activity in high southern latitudes is related to the activity in northern latitudes. Scintillation observations were made during the International Geophysical Year at the Royal Society Base, Halley Bay, Antarctica and have been compared with simultaneous observations made at Jodrell Bank in England. A full description of the methods and results of the Halley Bay observations have been given by BRENAN (1960) and the Jodrell Bank observations have been described by CHIVERS (1960) and earlier workers. The details of the programmes undertaken at the two stations are not important to the present discussion and need not be repeated here. It is necessary however to refer to the positions of the stations and their coordinates are listed in Table 1. It can be seen from this table that the mutual placing of the stations is not ideal for comparisons of the activity in the two hemispheres, although it is more nearly so than for any other pair of stations operating during the International Geophysical Year. This is because the longitude of Halley Bay is 24” west of Jodrell Bank and this corresponds to a phase difference in any possible diurnal variation of activity at the two places of nearly 2 hr. Neither are the stations ideally situated with respect to the geomagnetic field since it is at places at either end of a field line that especially high correlation might be expected (VESTINE, 1959). VESTINE has computed the conjugate points of a selected number of 287
Research notes Table
1.
Geographic coordinates
Station Halley Bay Jodrell Bank
75”31’S 1 “6”36’ I%53”14’ N 2”18’ W
Geomagnetic coordinates 65.8’ S 24.3” E 56.3” N 82.5’ E
stations using the observed magnetic field, and by interpolation of his results it transpires that the field line passing outwards at Halley Bay enters the ionosphere again in the vicinity of 54”N 22”W far to the west of Jodrell Bank. The Halley Bay scintillation observations used here are those of the Centaurus radio source made near the time of its upper culmination at Halley Bay. The data available at Jodrell Bank concerns the radio source in Cassiopeia which at that time bears approximately 3O”E of N of the station, and the line of
Jodrell Fig.
Bank
fluctuation
amplitude,
%
1. Correlation of scintillation amplitude at Jodrell Bank and Halley Bap (Nedian values and interquartile ranges).
sight to the source then passes through the ionosphere several hundred kilometres distant from Jodrell Bank at a point nearly 2000 km from the conjugate point of Halley Bay. The scintillation amplitude at Halley Bay at each upper culmination observation has been compared with the amplitude measured at the same time at Jodrell Bank. The correlation diagram is shown in the figure and the correlation coefficient is +0*37 for 388 pairs of observations. This is a statistically significant correlation. Moreover the correlation coefficient would probably have been higher still if it were not for the limitations that have been mentioned earlier. The physical significance of the correlation is less obvious and will be discussed next. Few results have been published on the day-to-day correlation of scintillation activity at stations separated by a few hundred kilometres, and they are restricted to places in the same hemisphere. Thus though LITTLE and LOVELL (1950), KOSTER (1958), STANLEY and SLEE (1950)and REID (1957) have all considered some aspects of the differences between the scintillation at distant stations only the first two publications refer to the question of whether scintillation can occur at one station without being detected at the other. 288
Research
notes
Using the data given by LITTLE and LOVELL for sixty-six observations of the Cassiopeia source it appears that the correlation coefficient relating the occurrence of scintillation at Cambridge and Jo&e11 Bank (210 km apart) was +O*SS. The correlation analysis made by KOSTER of the simultaneous occurrence of scintillation at Cambridge and Ghana showed that the activity was unrelated at the two places. The correlation coefficient between twenty-two pairs of observations was only $0.08. When these values are compared with the correlation coefficient + 0.37 derived from Halley Bag and Jodrell Bank data it appears that there is a closer connexion between the scintillation occurring at high latitudes in the two hemispheres than between that occurring at a high latitude and the equator. This suggests that there may be a distinction between the origin of equatorial and high latitude scintillation and the distinction is emphasized when the close correlation observed between high latitude scintillation activity and magnetic disturbances (DAGG, 1957a; CHIVERS,1960; BRENAN, 1960) is compared with the singular lack of correlation between equatorial scintillation activity and magnetic disturbances (KOSTER, 1958). It was the difficulty of explaining equatorial and high latitude scintillation together in a single theory that led DAGG (1957b) to reject the idea of an aurora1 origin of scintillation. The results quoted here however suggest that no single theory could be expected to account for both types of scintillation, and the demonstrated correlation between the activity at Halley Bay and Jo&e11 Bank strengthens the view that high latitude scintillation and aurora1 activity are closely associated. Acknowledgements-1 am grateful to Dr. H. J. A. CHIVERSfor providing the Joclrell Bank scintillation data. The work formed part of the programme of the British National Committee for the International Geophysical Year. P. M. BRENAN Xuffield Radio Astronomy Laboratories Jodrell Bank, University of Manchester REFERENCES BRENANP. M.
1960
CHIVERSH. J. A. DAGUM. DAGGM. KOSTERJ. R. LITTLEC. G. and LOVELLA. C. B. REID G. C. STANLEYG. J. and SLEE0. B. VAN hLEZr J. A. VESTINEE. H.
1960 1957a 195713 1958 1950 1957 1950 1959 1959
The Royal Society, I.G. Y. Antarctic Expedition, Halley Bay, Coates Land, Falkland Islands Dependencies, 1955-1959, Vol. 2. The Royal Society, London. In press. J. Atmosph. Terr. Phys. In press. J. Atmosph. Terr. Phys. 10, 194. J. Atmosph. Terr. Phys. 11, 133. J. Atmosph. Terr. Phys. 12, 100. Nature, Lond. 165, 423. Canad. J. Phys. 35, 1004. Au&. J. Phys. A 3, 234. J. Geophys. Res. 64, 1683. J. Geophys. Res. 64, 1411.
The magnetic storm-time variation of radio star scintillations and aurora1 radio echoes (ReceivedI September 1960) CONTINUOUS observations have been made at Jodrell Bank since the 1954 sunspot minimum, of radio star scintillations of the source in Cassiopeia and of radio echoes from the aurora
lo-(12pp.)
289