Indicate that the rate of flare production associated with any particular

indicate that the rate of flare production associated with any particular

Flares per day of importance higher than or equal to I is - R/25, where R is the supe number given by (5.2). Thus, if R = 100 on any day, four flares of importance 21 can be expected. Since subflares are several times more numerous, if these are taken into acov a flare every hour will be more natural.

 Since flares originate almost always within abow 100,000 km of a spot group, the flare distribution on the solar disk bears close correspondenc with the distribution of spot groups. Further, quantitatively, observations indicate that the rate of flare production associated with any particular spot group depends on the area A of the spot group and on the time rate of change of the area dAldt.

 A typical flare has a surface area 5 x 10 cm (assuming radius = 4 x 10° cm and circular shape) and a height of -2 x 10° cm so that the typical volume is - 1029 cm. The total energy outpu' for such a flare is - 2 x 104 erg, so that the average energy density in a flare is - 2 x 10 erg cm. Most of this energy Is emitted in corpuscular radiation. Although flares radiate in most of the frequencies of the electromagnetic spectrum, from X-rays and rrays to long-wavelength radio waves, and also relativistic particles (cosmic rays), most of the energy is emitted in X-rays and ultraviolet radiation. The energy emitted in optical range is not too large, may be about 10 per cent and that in radio waves and cosmic rays is insignificant.

 Like size and intensity, the spectrum of flares also differ greatly from one another. In large flares the continuum is strongly brightened, but in normal flares of moderate importance the brightening of the continuum is not very marked, except over a region surrounding H H itself is observed in strong emission with large symmetrical emission wings.

 The wings, however, fade away quickly after the onset of the flare, while the flare may still linger. The central intensity of H becomes three to four times that of the continuum and the width may be as large as 15 Á.