Not sure what vantage point you want.
If you are inside the atmosphere. The environment shader uses real world physics to simulate all the subtle effects for an entire atomsphere at any elevation. Just draw a polygon sphere around your seen and apply the shader as in the Rendering Dialog. Be sure Mental Ray is selected first, before you select shaders.
If you just need a faint halo around a globe from a distance, you can put a larger sphere around the clobe and then go to the material editor and then turn the material to constant, make it partially transparent, then play with the blur settings. This is similar to the "atom" lab in the Quick Start Guide. You can also apply the glow shader as a material shader on the globe in the Material Editor dialog.
Note: All the shaders should be in the MentalRay or effects databases. You may have to load them from the library CD first.
Hope this helps,
Urp