Journal of geomagnetism and geoelectricity
Online ISSN : 2185-5765
Print ISSN : 0022-1392
ISSN-L : 0022-1392
38 巻, 4 号
選択された号の論文の5件中1~5を表示しています
  • M. ROY, R. RAJARAM
    1986 年 38 巻 4 号 p. 231-238
    発行日: 1986年
    公開日: 2010/09/14
    ジャーナル フリー
    The problems encountered in estimating the inductive electric field from a combination of whistler data and simultaneous ionospheric measurement of the electric field are examined. It is shown quantitatively that the presence of time varying currents in the magnetosphere can produce large errors in estimating, from the whistler data, the electric fields in the region of the current flow. The distortions in the field lines produced by the currents make it difficult to infer the potential electric fields in the equatorial magnetosphere given the electric fields in the region of the ionosphere. Thus from the whistler and ionospheric observations during periods of magnetic activity, it becomes difficult to estimate the inductive and potential components of the electric field in the magnetosphere without an accurate knowledge of the current systems prevailing at the time of observations. Presence of large field aligned electric fields can prevent the use of the technique in the region of intense particle precipitation.
  • Takashi OKUZAWA, Takashi SHIBATA, Takumi ICHINOSE, Kazuyoshi TAKAGI, C ...
    1986 年 38 巻 4 号 p. 239-266
    発行日: 1986年
    公開日: 2010/09/14
    ジャーナル フリー
    Short-period disturbances of the ionosphere were observed by a network of HF Doppler receivers in central Japan at the time of typhoons 18 and 19 which crossed the Islands of Japan successively in September 1982.
    Both dynamic and static spectral analyses on sample records revealed that (1) these waves have the periods ranging between 1.4 and 9.7min that correspond to infrasound at F-layer heights (and partly to gravity wave at E-layer heights), (2) the spectral content varies from hour to hour, from station to station for a given typhoon, and further one typhoon to the other, and (3) the spectral fine structure does not accord with existing theoretical prediction for thunderstorms. It is, therefore, plausible that the observed spectral peaks arose from the characteristics of the radiation sources in the typhoon air mass.
    Horizontal and vertical phase velocities, and corresponding wavelengths of the ionospheric waves were also measured using cross-correlation method. It is shown that (1) the horizontal phase velocities take similar values to those observed during the severe thunderstorms and tornadoes so far reported, with scatter range of the values being slightly larger than the latter two, and (2) the mean values of the upward vertical phase velocities are several to ten times larger than those of the horizontal ones.
  • Hiroshi KUMAGAI
    1986 年 38 巻 4 号 p. 267-274
    発行日: 1986年
    公開日: 2010/09/14
    ジャーナル フリー
    The effects of geomagnetic activity on the mid-latitude scintillation have been investigated by using VHF radio waves from the geostationary satellite ETS-II. Statistics of nearly one-year data reveal that (1) geomagnetic activity dependence of the scintillation around Japan has properties similar to those of the equatorial scintillation; i.e., the occurrence tends to be suppressed with the increase in geomagnetic activity in summer (the season of high scintillation activity), especially in the premidnight hours, and (2) there is a negative correlation between Kp index and the scintillation occurrence in the range of 0≤Kp≤4, while the correlation becomes positive in the range of Kp≥5, so that we may have two peaks of the occurrence at Kp=1 or 2, and Kp≥8. The former peak depends obviously on season, whereas the latter does slightly. These results will give evidence that the scintillation tends to occur more frequently during severe geomagnetic storms in any season.
  • Takasuke SAKAI
    1986 年 38 巻 4 号 p. 275-278
    発行日: 1986年
    公開日: 2010/09/14
    ジャーナル フリー
  • K. KODAMA
    1986 年 38 巻 4 号 p. 279-284
    発行日: 1986年
    公開日: 2010/09/14
    ジャーナル フリー
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