Complex sentence: Solar flares affect all layers of the solar atmosphere (photosphere, chromosphere, and corona), when the plasma medium is heated to tens of millions of kelvins the electrons, protons, and heavier ions are accelerated to near the speed of light.
Split into simpler sentences: Solar flares affect all layers of the solar atmosphere (photosphere, chromosphere, and corona), when the plasma medium is heated to tens of millions of kelvins. The electrons, protons, and heavier ions are accelerated to near the speed of light.