stares are the most energetic phenomena of highly transient nature

stares are the most energetic phenomena of highly transient nature

Stares are the most energetic phenomena of highly transient nature occurring in the Sun. While observing the Sun on spectroheliograms or filtergrams, sometimes the chromospheric emission lines, particularly the H and K Ca II lines originating in the sunspot and surrounding clage regions are observed to brighten up intensely within a few seconds or minutes.

 Such corcurrences are known as flares. The intensity of emission lines increases as much as four to five timies of those originating in plages within a few minutes, and sometimes within only 10 res. (for microflares). The strengths of lines then decay raher slowly within a time interval of 10 to 100 minutes.

 A very large flare can also be observed in the white light of the Sun when it appears as an intense bright spot against the continuous background of the spectrum of the surrounding solar disc. Flares are believed to originate in chromosphere but rise far up into the lower corona.

 They have a tendency to occur near the complex groups of spots and usually the occurrence is repeated many times in the same place. Occasionally, they are seen to occur when a spot group is rapidly developing. Some of these have also been observed to occur from the umbrae of large full-grown spots with complicated magnetic field structures.

 These observations clearly associate ilares with sunspot activity. Flares are classified according to their brightness and the areas covered by them. The area seems to be more important criterion of classification because usually, the larger the flare the brighter it is and with longer lifetime.