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Volume 39, Issue 10
Displaying 1-5 of 5 articles from this issue
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Takashi AOYAMA, Hiroshi OYA1987 Volume 39 Issue 10 Pages 571-589
Published: 1987
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSA new station for the observation of solar decametric radio bursts has been developed at Miyagi Vocational Training College in Tsukidate, Miyagi, Japan. Using the swept frequency radiospectrograph covering a frequency range from 20MHz to 40MHz within 200 msec, with bandwidth of 30kHz, the radio outbursts from the sun have been currently monitored with colored dynamic spectrum display. After July 1982, successful observations provide the data which include all types of solar radio bursts such as type I, II, III, IV and V in the decametric wavelength range. In addition to these typical radio bursts, rising tone bursts with fast drift rate followed by strong type III bursts and a series of bursts repeating rising and falling tone bursts with slow drift rate have been observed.View full abstractDownload PDF (9676K) -
Part II: Plasma Density across the PlasmapauseHiroshi OYA, Takayuki ONO1987 Volume 39 Issue 10 Pages 591-607
Published: 1987
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSThe electron number density across the plasmapause was accurately measured using an RF sounder on board the Jikiken satellite, which was launched from Kagoshima Space Center in Japan on September 16, 1978, into an orbit with the initial apogee of 30, 051km and the perigee of 227km. The electron number density was determined by observing plasma resonances such as the electron plasma resonance (FP), the electron cyclotron resonance (nFH) and the upper hybrid resonance (FUHR), which were not affected by the turbulences surrounding the satellite. The electron number density outside of the plasmapause showed values greater by one order of magnitude than the previous observations using particle detectors. Outside the plasmapause in the dayside region, there is a good agreement with an L-4 relationship in the electron number density profile, as is consistent with a large inflation of the plasma due to a supply from the ionosphere. The location of the plasmapause has been examined as a function of the geomagnetic activity including the dead calm state. Two types of irregularities were found in the electron number density profiles crossing the plasmapause: i) a large scale irregularity with the characteristic scale in L values of 0.1-0.5 (600-3000km) in the plasmasphere and ii) an irregularity with smaller scale sizes near the plasmapause.View full abstractDownload PDF (2993K) -
Takasi OGUTI, Rumi NAKAMURA, Tatsundo YAMAMOTO1987 Volume 39 Issue 10 Pages 609-624
Published: 1987
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSOn the basis of all-sky TV records of auroras, faint auroral patches (nonpulsating in luminosity) are found to oscillatorily drift associated with concurrent magnetic pulsations on the ground. These oscillations in the drifts of auroral patches are found to be consistent with the oscillations in the electrostatic electric field associated with the concurrent magnetic pulsations. This implies that these magnetic pulsations are brought forth by ionospheric electric currents which are produced by electrostatic electric fields associated with shear Alfven waves in the magnetosphere. The result, therefore, indicates that the simultaneous measurement of the drifts of auroral structures at the time of ground magnetic pulsations is a convenient method of examining whether the magnetic pulsations are really ascribed to HM wave fields propagating down from the magnetosphere, or if they are essentially caused by the change in conductivity inhomogeneity in the ionosphere. It is also shown that the azimuthal phase speed (wave length), as well as the oscillation amplitude, highly varies from the dayside to the evening, i. e., it is larger in the dayside and becomes much smaller toward the evening sectors. Theory must take this steep longitudinal non-uniformity into consideration.View full abstractDownload PDF (2244K) -
P. C. OZOEMENA, C. A. ONWUMECHILI1987 Volume 39 Issue 10 Pages 625-636
Published: 1987
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSA method of analysis has been used to obtain electrojet parameters from the POGO Satellites' data during the solstitial seasons. This yields enormous values about 432 each, of electrojet's halfwidth w, peak eastward intensity J0, and total eastward current I+, -covering the entire 360° longitudes round the earth, and within 6 hours of local day time in the December and June solstitial months of the years 1968 and 1969 respectively. The daytime all-longitude averages of these parameters for the combined solstices are: (226±11)km for w, (207±28) Akm-1 for J0 and (51±7)×103 A for I+. This second coverage of the earth, with a new set of data, shows that J0 and I+ vary considerably with longitude, unlike w, which remains fairly constant throughout the globe. Interestingly, we find that, apart from the expected maximum in J0 and I+ around longitude 280°E, subsidiary maxima also occur at about 100°E, and 190°E, in confirmation of the equinoctial results of ONWUMECHILI and AGU (1981). It is suggested that the longitudinal variations in J0 and I+, may arise from the longitudinal differences in conductivities, wind systems and possibly changes in electric field at electrojet altitudes.View full abstractDownload PDF (974K) -
Hideki MURAKAMI, Hitoshi MIZUTANI, Sachio NABETANI1987 Volume 39 Issue 10 Pages 637-638
Published: 1987
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSDownload PDF (114K)
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