[petschge]

Expressing all quantities as small multiples of suitable reference quantities is quite common. The resulting equations after simplifications are often referred to as dimensionless (because the reference quantity has absorbed the units and only a small dimensionless number remains).

There is two upsides to this: 1.) All quantities are order one, safely away from underflow and infinity. 2.) The equations are generally simpler, which was important when the many limitation in simulation codes was flops, not memory bandwidth.

There are also important downsides: 1.) You have to manipulate the equations before you start coding. Porting features from a code that used another normalization is quite error-prone. 2.) All quantities are order one, which makes it hard to detect if you accidentally use and electric field instead of a magnetic field. All you see is a number of roughly the correct magnitude. 3.) Comparison between codes is more difficult, in particular if the use different normalization, because you have to convert from "code units" to actual SI units.