[i speak in math]

Then, from the pen tool sub menu, choose the convert point tool. Start at the top by clicking on the end point and dragging with your line to make the path a smooth curve.



Once you have a nice curve, choose the brush tool. Set it to size 40, the color white, and make sure you have shape dynamic and smoothing enabled.



Now you're ready to make it glow. Choose your convert point tool again (actually many tools can be used for this step). With your new layer selected, right click on your image and choose stroke path. Make sure to choose simulate pressure then press okay.



If you notice any corners or spots that don't look right, step back or undo and fix the curve with the direct selection tool.