Consider a sheet of paper, when you crumple it, that is Ahankar (ego). As you slowly open the sheet and try to lay it flat as it used to be, that form is called Aatma.

In Yoga, they refer to this concept as Chitta Vritti Nirodha. If you take a string and knot it at several locations (Ahankar), the process of removing each knot is through Gyan (knowledge) and the knot-free string thus obtained, is the Aatma. One attains it through Aatma-gyan.

So the spectrum of Aham (one's identity) and Aatma (Consciousness), is such that you move from Ahankar (ego) towards Aatma, upon obtaining Aatma-gyan (self-realization).