The layer’s parameters:
Blending Options>Gradient Overlay
Gradient’s parameters: 
The next layer supposes making one more circle. Firstly we need to apply the
Ellipse Tool (U) to represent the outside edges and then press
Alt button to cut out the inside part, applying the last instrument too.
The layer’s parameters:
Blending Options>Gradient Overlay
Gradient’s parameters:
Blending Options>Stroke
