There used to be a brush I was fond of in Photoshop CS5 that was shaped like a vertical line, called "Aurora" or something like that. It was preset to draw northern lights nicely. Is there any way I can find this brush in Photoshop CC now, or will I just have to find and download something similar from online?
Easy-peasy to make.
Open a new document.
Create a new layer.
Use the rectangular Marquee tool to make a tall thin selection.
Make the foreground colour about 50% grey, and background colour white.
Run a gradient down your selection
Turn off the selection, and put a tiny black dot at the top.
Define it as a new brush preset.
That's it. You might want to reduce opacity, and you could play with other settings like making Angle Jitter control to Direction. You will need to set brush spacing as low as it will go for that at 1%.