Is the material in the Sun uniformly homogeneous?
No. The Sun contains a central core where the nuclear reactions take place. The core is surrounded by a radiative zone through which the energy radiates outwards from the core. The next layer is the convective zone which is in constant turmoil and heat transfer takes place by convection. The final layer is the photosphere which is the outer shell of the Sun (which we see which radiates light, heat and other forms of energy into space.
The cross-section consists of the core, radiative zone and convective zone. The visible surface is the photosphere on which are seen the dark sunspots and the bright faculae. Above this lies the chromospheres, and then the hot rarefied corona. The stream of subatomic particles moving out through the corona into space is the solar wind.
What is the corona?
The corona refers to the outermost regions of the Sun’s atmosphere. The corona can be seen from Earth only during a total solar eclipse, or by using an occulter-a disc used on the telescope to block the view of the sun’s disc (photosphere).