TEMPORAL AND SPATIAL CHARACTERISTICS OF SOLAR-FLARES FROM OBSERVATIONS

Temporal and spatial characteristics of solar flares are briefly reviewed in this paper. The global, temporal and spatial behaviours of flares are given first. Besides the 154-day periodicity, an 80-day periodicity of occurrence rate of large hard X-ray bursts for the period 1980 February - 1985 December, and the delay of the peak occurrence rate of large flares are pointed out, then the gregariousness of major flares is shown. In the third section, the time process and spatial structure of individual flares are shown and described according to space and ground-based observations. In the last section two problems on flare properties are discussed. (i) Previous classifications of solar flares are based generally on observations in a single spectral region. A new classification of flares based on observations in multi-spectral regions is given. (ii) Energy released in part of a loop seems to be not enough for a whole flare, and a qualitative model in which the energy is supplied by the untwisting of magnetic fields is proposed.