Particles leave the influence of solar gravity
A vast range in size and brightness is observe among flares and their importance is assigned accordingly. The importance is labelled 1, 2, 3 and 3 according as the areas covered by the flare lie in the ranges 100-250, 250-600, 600-1200 and 1200 respectively, which are measured inunts of a ailidntf part of the sotar disk. Besides the above classes, there are oflares iubelled with mporance and the microflares. Aithough the flare statistics partly depend on the observer, rough analysis indicate that about 80 per cent of flares are of importance I and about 3 per cent are of importance 3, while the remaining flares are of importance 2, the flares of importance 3" are of extremely rare occurrence.
Flares, are events of frequent occurrence in the Sun and if we include subflares, there may be one flare every hour but flares of importance 3" hardly occur even once in a month. Flares are correlated with sunspot activity and the number of flares is observed to bear an approximate mathematical relation with the number of sunspots. It is found that the number.
Particles leave the influence of solar gravity and after a certain period depending on their speeds, impinge on the Earth's magnetosphere giving rise to geomagnetic storms and aurorae. This phenomenon, commonly known as solar wind, will be discussed in greater details in the Jast section of this Chapter. As we have already mentioned, solar flares are always accompanied by enhanced X-Tay and ultraviolet radiation.
The first X-ray measurements during a flare were performed by H. Friedman in 1956 by sending rockets to heights in the range of 60 km. These data were extended by several other flights in subsequent years.
Such measurements, in general, show two components of X-ray radiation: (a) a less energetic slow component lasting for a longer time; usually of order of an hour, and (b) a sudden short-lived high energetic component lasting for a few minutes. The first component originates from natural transitions in the coronal gas heated by flares to a temperature - 5 x 10 K. The second component is associated with bursts of nonthermal emission.
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