How to create a nice effect with just a sinus

Black Background

Start a new comp (Ctrl+N) Select the main composition on the top of the tree and uncheck "Alpha Layer" to have a black background, it won't change anything, it is just a matter of aesthetics.

Create Particles

Create a Particles Simulate a particle system Read More system with 3D Layers>Points>Particles.

Set the particles system like a boss

Just do as on the pictures ... trust me....

Opacity Sinus

Add a Opacity Change the opacity of the geometry vertices using an input attribute Read More modifier preset named "Flicker" over the particles Right Click->Modifiers->Attributes->Opacity->Flicker

Little Explanation and conclusion

Now you can disactivate/activate the particles systems to see a nice effect
As you may also see if you take the time to expand the Opacity Change the opacity of the geometry vertices using an input attribute Read More modifier is that this preset is set with a Age vertex mask and that particles opacity will vary between 0% and 100% over it's lifetime following a sinus curve repeated 3 times. Good job old chap, you made it !