Diagnostics of the heliosphere by means of ground-based ULF observation

ULF waves have been utilized for diagnostics of the earth\u27s magnetosphere since the 1960\u27s. Similarly, an attempt is given in the present paper to diagnose the magnetosphere of the sun by utilizing the ULF waves observed at the Onagawa Magnetic Observatory. The diagnostics is based on the observed high correlation among the solar wind speed, amplitude and duration of Pc 3,which is the so-called sensitive anemometer for the solar wind. We selected the two extremes of distinct 27-day recurrence time patterns : the vertical pattern in 1974 and the horizontal pattern in 1954. From the vertical pattern, we diagnose the heliosphere with a tilted neutral sheet, which is the representative feature for the excursion phase of a solar cycle. While, the analysis of the horizontal pattern derives the heliosphere with a less-warped neutral sheet near the equatorial plane. This is the representative configuration of the heliomagnetospheric neutral sheet in the aligned phase. The two representative sheet configurations are discussed in terms of the solar cycle variation of the heliosphere

Non-Seasonal Annual Variation in the Period of Pc 5 Observed at Syowa Station (d. ULF Waves in the Magnetosphere) (Proceedings of the Second Symposium on Coordinated Observations of the Ionosphere and Magnetosphere in the Polar Regions : Part I)

ULF signals registered at Syowa Station are reproduced by an FM tape recorder with a speed-up ratio of 2×10^4 and are analyzed with a high-speed spectrum analyzer called HISSA. The Pc 5 periods in June, 1973, are revealed to be shorter than those in December, 1973. An eye-reading analysis of Pc 5's on the correlation chart obtained at Syowa Station from 1974 to 1977 shows also such annual variation in which the June periods are shorter than the December periods. These annual variations are regarded to be non-seasonal, since all Pc 5 period at Byrd, Pc 4 period at Fredencksburg, and whistler dispersion at Stanford exhibited the same annual variation as that at Syowa Station independent on the local seasons of these stations. These observed results are examined by three models, sun-earth distance model, conjugate point wandering model, and Φ-φ model