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Volume 26, Issue 1
Displaying 1-11 of 11 articles from this issue
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Yasunobu IWASAKA, Haruo HORII1974 Volume 26 Issue 1 Pages 1-12
Published: 1974
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSThe CO2 density profile is decided using the photochmical-eddy diffusion model, and the cooling rate of CO2 15μ band in the lower thermoshere is discussed. These results show that the cooling rate of 15μ band decreases somewhat in comparison with the estimation using the assumption of constant mixing ratio of CO2. The O2(1Δg) density profile which is simultaneously calculated has small second peak near 85km.View full abstractDownload PDF (1088K) -
R. K. MISRA1974 Volume 26 Issue 1 Pages 13-21
Published: 1974
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSThe characteristics of the horizontal drift vector in the F-region over the equatorial station Thumba around the times of morning and evening reversals are discussed in detail. The fading of the reflected signal is found to become extremely slow at these timings and the usual spaced antenna technique of determining the horizontal drift is found to be not applicable. The drift vector shows a more or less sudden reversal of direction and there is no indication of its going through north-south in the intervening time. The morning reversal of drift is found to occur at a time when the transverse size of the F-region irregularities is maximum, while the evening reversal shows a close correspondence with occurrence of the maximum virtual height (h′F) of the F layer.
The appearence and disappearence of the sporadic-E layer at Thumba is also found to be dependent on the timings of F-region horizontal drift reversal. The sudden reversals of the drift in the F-region during day time is also found to result in the disappearence of Es ionization at Thumbe for the corresponding short period. Both these effects are well correlated to the changes in the electrojet current direction.View full abstractDownload PDF (805K) -
Y. HONKURA, S. OSHIMA, T. KONDO1974 Volume 26 Issue 1 Pages 23-37
Published: 1974
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSTime-varying magnetic fields were recorded during the winter of 1972 with an array of 5 flux-gate magnetometers on Hachijo-jima Island. The observed records show a typical island effect, e. g. a reversal of sign of the vertical magnetic fields between the northern and southern observation points on the island when the inducing field varies in the north-south direction. The period dependence of the anomaly is examined for a period range from 5 to 240min by making use of the transfer function technique. A uniform period dependence is seen throughout the stations for periods longer than 30min or so. As a result it is shown that the geomagnetic variation anomaly on Hachijo-jima Island is accounted for by the central Japan anomaly superposed on the island effect, and the strong period dependence is due to the central Japan anomaly.
A numerical calculation of induced electric currents and magnetic fields is made on the basis of a non-uniform thin sheet model representing the island. As for transfer function Au, the calculated values are about twice as large as the observed ones as is the case for Miyake-jima Island (HONKURA, 1971). It is concluded, therefore, that a highly conducting layer must lie very close to the earth's surface underneath Hachijo-jima Island.View full abstractDownload PDF (1314K) -
R. D. HIBBS, F. W. JONES1974 Volume 26 Issue 1 Pages 39-53
Published: 1974
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSElectromagnetic induction in a two-dimensional earth by a non-uniform, spatially varying, aperiodic current source is considered. The two-dimensional diffusion equation (for the E-polarization case) is solved by a separation of variables and is related to the current source by a Fourier integral which synthesizes the actual fields from elementary fields with time dependence exp (iωt) over a horizontally stratified earth. An aperiodic source is obtained by summing the single frequency solutions in a Fourier transformation. The spatial variation is achieved by superimposing the electromagnetic fields of separate aperiodic, non-uniform current sources which vary independently with time. Variations of the magnetic field components with time at the surface of the earth are studied.View full abstractDownload PDF (1110K) -
Robert F. BUTLER, Allan V. COX1974 Volume 26 Issue 1 Pages 55-71
Published: 1974
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSThe effects of neutron irradiation on remanent magnetization in multidomain iron and kamacite (3wt% Ni) samples of varying initial coercivities were investigated in order to determine whether cosmic ray exposure significantly affects the natural remanent magnetization (NMR) of lunar samples and chondritic meteorites. Irradiation to 1017 fast neutrons/cm2 increased bulk coercive force (Hc) by an average of 15%. Annealing for 1 hour at 200-300°C returned Hc to its pre-irradiation value. The dominant effect of irradiation on remanent magnetization was to decrease the total intensity by 5-45%. AF demagnetization spectra of both isothermal and thermal remanence before and after irradiation indicate that neutron bombardment slightly increases the resistance to AF demagnetization. No similar increase in resistance to thermal demagnetization was indicated. The changes in Hc and AF demagnetization spectra are attributed to radiation induced point defects rather than to pinning of domain walls by vacancy clusters and dislocations. The NRM in chondritic meteorites and most lunar samples is too stable to be accounted for by exposure of isothermal remanence to cosmic rays. Thus the NRM must be some form of thermal or thermochemical remanence.View full abstractDownload PDF (1936K) -
R. K. VERMA, G. S. MITAL1974 Volume 26 Issue 1 Pages 73-78
Published: 1974
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSDownload PDF (562K) -
Shigeru MIYAZAKI1974 Volume 26 Issue 1 Pages 79-81
Published: 1974
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSDownload PDF (257K) -
Czang-go BAAG1974 Volume 26 Issue 1 Pages 83-86
Published: 1974
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSDownload PDF (422K) -
D. E. WINCH1974 Volume 26 Issue 1 Pages 87-94
Published: 1974
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSDownload PDF (599K) -
S. P. GUPTA, A. K. SINGH, V. SINGHAL, B. A. P. TANTRY1974 Volume 26 Issue 1 Pages 95-100
Published: 1974
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSOn some nights atmospheric waveforms were recorded simultaneously at Gulmarg and Varanasi. From the frequency spectra observed at these two stations, relative attenuation coefficients in the frequency range 1-20kHz were obtained using the mode propagation theory. Attenuation factors showed a maximum around 3kHz and minimum around 8-13kHz. The implications of these results are discussed in detail.View full abstractDownload PDF (552K) -
P. S. NAIDU1974 Volume 26 Issue 1 Pages 101-104
Published: 1974
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSDownload PDF (229K)
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