Solar Phys). An exceptional variety of positions and polarizations was found for two type I storms and numerous sporadic bursts observed during 15 con secutive days with the Culgoora radio-heliograph at 80 and 160 MHz. The main observational points for the type I storms are as follows: (Al) The type I storm centres were not situated radially above the associated sunspots but were displaced systematically northwards. (A2) They did not always show a uniform daily motion across the disk. The

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... storm, in particular, shows anomalous movements between 1972 October 27 and 30. (A3) The sense of circular polarization of the storms was left-handed (L.H.) and remained so as the sources rotated across the disk, except on one day, October 30, when the L.H. polarized source was accompanied by a right-handed (R.H.) polarized companion at both 80 and 160 MHz. In addition to the persistent storm centres a large number of sporadic bursts oc curred. These were mainly of types III and V, with some showing inverted-U struc ture. The sporadic bursts generally showed a variety of temporal and spatial distribu tions, particularly at 80 MHz. One sequence of such bursts observed at 80 MHz between 00 h 37 m and Ol^S" 1 UT on 1972 October 29 is illustrated in Figure 1 . Some remarkable features shown by the group of the sporadic bursts are the following: (Bl) All sources except No. 2 appeared to lie on an arc extending around the active region in which the associated Ha-flare occurred. (B2) Irrespective of spectral type all the sources were weakly L.H. circularly polar ized. (B3) No sequence was evident in the positions of successive bursts. (B4) Sources showing different spectral features usually appeared at different places. The two-frequency radioheliograph data are combined with optical data to derive a model of the coronal magnetic field structure for this complex of active regions. In attempting this we assume that (a) type I storms occur in the stronger magnetic fields of active regions, probably in magnetic fields forming closed loops; (b) sporadic bursts are associated with weaker magnetic fields; when bursts have inverted-U structure their exciting agencies (electrons) are guided around closed * On leave from Tokyo Astronomical Observatory, University of Tokyo.