Journal of geomagnetism and geoelectricity

Dispersive Motions in the F-Region of the Equatorial Ionosphere

D. K. BAMGBOYE

1973 Volume 25 Issue 3 Pages 237-247
Published: 1973
Released on J-STAGE: March 12, 2010

DOIhttps://doi.org/10.5636/jgg.25.237

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Some results of “dispersion” analysis of F-region drift data obtained at Ibadan (dip 6°S) are presented. On a number of occasions marked dispersion involving a velocity variation of about 60 msec^-1 or more from low to high fading frequencies has been found. The results suggest that in the “correlation” analysis the “apparent” velocity probably measures the motion better than the “true” velocity, whether or not dispersion is present. It is also found that the motions occurring at this latitude are not always in the east-west direction. Occasionally, two independent motions corresponding to different fading frequency ranges and moving at right angles to each other may be involved.

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Returning Flow of the Equatorial Electrojet Currents

Akira SUZUKI

1973 Volume 25 Issue 3 Pages 249-258
Published: 1973
Released on J-STAGE: March 12, 2010

DOIhttps://doi.org/10.5636/jgg.25.249

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A distribution of return currents of the equatorial electrojet was calculated by solving the partial differential equation, div J_e=0, under the condition of non-uniform distribution of ionospheric conductivity and the boundary condition at the equator which was deduced from ground magnetic variations. It is found that the return currents decrease rather quickly with increasing distance from the equator. Comparing the distribution of the return currents with that of the Sq currents, it is concluded that the contributions of the return currents to the ground magnetic variations are mostly less than ten and rarely twenty per cent of those of the Sq currents, at any point except in small areas just under the current vortices.

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A New Analysis of the Geomagnetic Sq Field

Akira SUZUKI

1973 Volume 25 Issue 3 Pages 259-280
Published: 1973
Released on J-STAGE: March 12, 2010

DOIhttps://doi.org/10.5636/jgg.25.259

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The geomagnetic solar quiet daily variation field, Sq, was analyzed by a new method and the result was compared with that of MATSUSHITA and MAEDA (1965). The new method is intended to avoid errors which occur in harmonic analysis due to the equatorial electrojet of narrow latitudinal width; the magnetic effect originating from equatorial electrojet currents is temporarily omitted until after the spherical harmonic analysis has been performed, and later the effect is added in. Compared with the results obtained by Matsushita and Maeda, it is found that: (1) Spherical harmonic coefficients for the Sq field generally become smaller. (2) Magnitude of the equivalent current systems external to the earth diminishes by 10-20 per cent. (3) The coefficients which are mainly responsible for the jet effect are a¹₆, a¹₁₀, b¹₆, b¹₁₀, a²₇, a²₁₁, etc.; they become considerably smaller. In many of these terms the amplitude ratio E^m_n/I^m_n of the external to the internal part also becomes smaller. (4) The amplitude ratios, E^m_n/I^m_n, for main terms become larger.

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Rocket Observation of Twilight Airglow in the Near Infrared Region

Satio HAYAKAWA, Koji ITO, Toshio MATSUMOTO, Tetsuo NISHIMURA

1973 Volume 25 Issue 3 Pages 281-296
Published: 1973
Released on J-STAGE: March 12, 2010

DOIhttps://doi.org/10.5636/jgg.25.281

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Twilight airglow emissions in the wavelength ranges at about 1.3μm, 1.7μm and 2.2μm were observed by a rocket-borne photometer. The heights of the airglow layers and the local times at emission regions were derived taking into account the roll, precession and altitude of the rocket. The volume emission rates in these three bands were peaked at about 73km. The mean lifetime of the O₂(¹Δ_g) molecules was obtained to be 33±2 minutes from the time variation of the airglow intensity in the 1.3μm band. This is accounted for in terms of a combination of the spontaneous decay and the collisional deexcitation. The rate constant for the latter is about a half of that obtained in laboratory measurements at room temperature.

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Guidance of Whistler Waves in the Magnetosphere, Along Field-Aligned Irregularity with a Quartic Distribution of Ionization Density

Takashi OKUZAWA, Kaoru YAMANAKA

1973 Volume 25 Issue 3 Pages 297-312
Published: 1973
Released on J-STAGE: March 12, 2010

DOIhttps://doi.org/10.5636/jgg.25.297

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A numerical study is made on the ducted-whistler propagation in the magnetosphere by using the phase-integral technique. The guidance in the present model takes place along a dipole field-aligned irregularity with a slowly varying, quartic distribution of ionization density. Numerical calculations are made on the track widths, the mode angles, and the travel times of trapped modes for a wide range of irregularity parameters. Calculations are carried out for a field line for which the shell parameter L=2, Angerami and Thomas's model of ionization density being employed as a background component of the plasma distribution. It is shown that an increase in the transverse size of irregularity may not be responsible for the increase in whistler diffuseness.

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Electromagnetic Waves in an Inhomogeneous Anisotropic Medium of the Model Ionosphere

Masayoshi MAMBO, Isamu NAGANO

1973 Volume 25 Issue 3 Pages 313-323
Published: 1973
Released on J-STAGE: March 12, 2010

DOIhttps://doi.org/10.5636/jgg.25.313

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Electromagnetic fields of a wave propagating in the ionospheric D region with its wave normal directing vertically upwards can be described by the Weber function. The model ionosphere pertinent to the present investigation is composed of the parabolic electron density profile with a constant collision frequency and the vertical magnetic field. The distribution of wave electric field intensity, reflection, transmission and conversion coefficients are numerically calculated. It is shown that the reflection coefficient for the right handed circularly polarized wave has a spirally diminishing characteristic in the amplitude-phase polar coordinate plane for increasing wave frequency. The left handed circularly polarized wave is reflected below the altitude where the wave frequency approaches to the penetration frequency. It is also found that the conversion coefficient of the transmitted wave decreases abruptly above a specific value of collision frequency.

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A Sheath Resonance Observed by a High Frequency Impedance Probe

Takehiko Aso

1973 Volume 25 Issue 3 Pages 325-330
Published: 1973
Released on J-STAGE: March 12, 2010

DOIhttps://doi.org/10.5636/jgg.25.325

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A complex impedance of a negative cylindrical probe in a magnetoplasma is calculated using a gradient sheath model, and quantitative values of the sheath resonance frequency for a floating probe are determined for various values of plasma parameters. Calculated results are in good agreement with the experimental data of a rocket borne impedance probe.

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Partial A. F. Demagnetization Studies of 40 Meteorites

E. E. LARSON, D. E. WATSON, J. M. HERNDON, M. W. ROWE

1973 Volume 25 Issue 3 Pages 331-338
Published: 1973
Released on J-STAGE: March 12, 2010

DOIhttps://doi.org/10.5636/jgg.25.331

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