This is a really simple tutorial on how to make auroras. This is great for darker sigs or images with lots of color.

Final Result

First Step:

Make the sig or background you want (or you can get a picture of the night sky or some kind of picture of a dark theme).

This is the image I used for this tutorial :

Second Step:

Make a New Layer.

Third Step:

Make a all Black layer with a brush.

Fourth Step:

Click on Filter > Render > Difference Clouds

Fifth Step:

Hit the CTRL+F about 6 times.

Sixth Step:

Change the Blending Mode to Color Dodge.

Seventh Step:

Click on Filter > Blur > Motion Blur

Eighth Step:

Use these Settings after you have Clicked on Motion Blur.

Ninth Step:

Duplicate that layer. Do this by Right Clicking the Layer.

Tenth Step:

You can hit CTRL+U to mess around with the settings and colorize it. To colorize it Check Colorize.

This is my final result (I did not colorize it because personally I like the way it looks right now).

Final Result: