Breaking this image down into the various elements you have the particles themselves, depth of field and motion blur.  To replicate this you would need to build up your image in layers.  Paint some random dots of various sizes onto a new layer.  Duplicate, rotate and move these layers to speed up the process.  Apply gaussian blur to some layers and motion blur to others, then erase anything that you need to in order to get the result you want.  Change the colour shading and opacity of the layers containing the particles furthest from the camera.  Doing this will create an image very similar to the one you posted.

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