Start with a new RGB image with black
background and lightblue foreground ground.
Add a new layer.

Draw a circle with the marquee tool and select the
gradient tool with the settings shown in the
picture here to the right.

Place the cursor in the top left of the circle
and drag it to the down right.

Apply the layer style inner 
shadow with  these settings.

Apply the RENDER/LENSFLARE filter with default settings.