USO
 
 
 

Characteristics of Flares

 

A solar flare is a transient phenomenon characterized by a catastrophic release of energy over a localized area on the solar surface. Energy of the order of 1032-1033 ergs may be liberated in a short span of a few minutes to an hour in major flares. Flares give rise to both electromagnetic and particle emissions. The electromagnetic flare radiations include almost the entire wavelength range from γ-rays,  X-rays, extreme ultraviolet to optical and radio waves.
In the optical region, solar flares are best seen in the chromosphere, using bright monochromatic radiations from hydrogen (H-alpha) and ionized calcium atoms (K-line of Ca+). Flares occur in a wide variety of shapes, sizes and intensities. Generally, chromospheric flares first appear as small bright points of about 4-5 thousand kilometer size and then in a very short time of a minute or so, suddenly a very large area (about 3 billion square kilometers in large flares) brightens up. Temperature of the flaring region can reach even to several million degrees. Flares generally tend to occur in active regions. Very intense flares can be seen even in white light (i.e. in photosphere). There is also a close link between energetic flares on the Sun and the terrestrial environment. The magnetosphere and the ionosphere of earth are disturbed by electromagnetic radiations and energetic particles released in flares, and effects such as, magnetic storms, aurorae and disturbances in long distance radio communications are observed.
The Linked sections illustrate various aspects of flares and their association with active regions.