著者

MUKHERJEE G. K. RAJARAM Ramaswamy

出版者

地球電磁気・地球惑星圏学会

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.34, no.11, pp.619-632, 1982

被引用文献数

1

---

The seasonal variations of the plasma dynamics have been investigated using Mead-Fairfield model. It is shown that shifts in the mirror points and meridional drifts are introduced as a result of the season dependent tilt of the dipole axis with the earth-sun line. Other parameters like radial and azimuthal drifts and the bounce periods are free from seasonal variations. The maximum shift in the mirror points and latitudinal drifts are produced in particles bouncing close to the equator but the former peaks in the mid-night meridian while the latter maximises (in magnitude) in the dawn and dusk sectors. A theoretical estimate has been obtained for the seasonal geomagnetic variation associated with these distortions of the ring current. It is shown that the seasonal variations in the declination can be accounted for if the ring current radius is taken as 7 earth radii.

著者

OGAWA Toshio TANAKA Yoshikazu MIURA Teruo YASUHARA Michihiro

出版者

地球電磁気・地球惑星圏学会

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.18, no.4, pp.443-454, 1966

被引用文献数

69

---

A simple observing system for the measurements of vertical electric field component of natural ELF and VLF electromagnetic noises by using ball antennas is described. With this system it is possible to measure long traveled natural ELF noises discriminated from natural local noises due to such as atmospheric electric space-charge fluctuations. Some of the typical recorded noises are shown. Observed ELF noises are divided into three characteristic types; “ELF flash”, “ELF burst” (N-and Q-types), and “ELF continuous”. ELF flashes originate from the lightning discharges in the area within about 1, 000km from the observing station. Occurrences of ELF bursts are more frequent in the daytime than in the nighttime, and are characterized by sudden increase at the time of local sunrise, suggesting the related mechanism of their generation to the solar position relative to the earth. N-type bursts are followed by VLF noises. Source distances of these bursts which are followed by tweek-type atmospherics in the night are estimated to be in the range from 2, 500km to 5, 000km. Q-type bursts often show clear oscillations of the frequencies of Schumann resonances. The daily variations of the mean amplitude of “ELF continuous” which composes the background noises are quite similar to the daily variations of the world thunderstorm activity.