Sup Demi. Good to have you back homie. What did you think of the NBA Draft?
Now to business:
I would argue that his cells are protected. Hence why he never gets sick. There were times where he drank poison. Inhaled fire, taken a bite out of a rock etc. The theory I was always familiar with was that his cells became supercharged and each one emitted the aura.
His cells eminate the biomatrix.
The biomatrix is a byproduct of a biochemical process. When his cells metabolize the metaprotein created from absorbing and metabolizing sunlight and radiant cosmic emissions, the biomatrix is created as a byproduct of this process, meaning when the protein is being broken down, the stored energy is released and creates an energy retentive field around Supes body as a side effect. The catalyst for this biochemical process within the cells can be destroyed by Iceman because using his powers, and riding the lines of Superman's own body composition, he can destroy the cellular peptides in Supes by removing or freezing all moisture in his cells, which would in turn cause this biochemical process to halt and short out Supes "forcefield" (or better yet, "energy field).
Supes cells need moisture, his absorption of sunlight allows him to sustain himself without food and contain the fluids within him from evaporating or being expelled due to overheating (sweating), leaving him without need to replenish them at most times. If all moisture were removed from his organic being, he'd lack cellular cohesion and the ability to faciltate his bodily functions down to a cellular level, being reduced to his base elements.
Basically, he'd be like dehydrated, powdered milk, but in this case, Powdered Kryptonian.