AEROGRAPHER'S MATE 3 & 2 



SUN 



The sun may be regarded as the only cource 

 of heat energy that is supplied to the earth's 

 surface and the atmosphere. All weather and 

 motions in the atmosphere are due to the energy 

 radiated from the sun. 



The sun, with a surface temperature of about 

 6,000° K (10,300° F), radiates electromagnetic 

 energy in all directions. The earth intercepts 

 about one two-billionths of this energy. Most 

 of the electromagnetic energy radiated by the 

 sun is in the form of light waves. Only a tiny 

 fraction is in the form of heat waves. Even 

 so, better than 99.9 percent of the earth's heat 

 is derived from the sun in the form of radiant 

 energy. 



Solar Composition 



The sun may be described as a globe of 

 gas heated to incandescence by thermonuclear 

 reactions from within the central core. (See 

 fig. 12-1.) 



The tremendous heat (or energy) generated 

 within the sun's core is transported by the 

 radiative transfer of photons (a measurement 

 of gamma radiation), which bounce from atom 

 to atom, similar to bouncing balls, through the 

 radiative zone. Within the convective zone, which 

 extends very nearly to the sun's surface, the 

 heated gases are raised buoyantly upwards with 

 some cooling occurring and subsequent convective 

 action until the gases are cooled to approxi- 

 mately 6,000° K (Kelvin or Absolute) at the 

 sun's surface. 





SOLAR 

 ATMOSPHERE 



SOLAR SURFACE 

 TEMPERATURE 

 APPROX. 6,000°K 



PHOTOSPHERE 



RADIATIVE ZONE 



CENTRAL CORE 

 (THERMONUCLEAR 

 REACTIONS) APPROX. 

 14,000,000° K 



Figure 12-1. — One-quarter cross/section depicting solar structure. 



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