@Override
    public void influenceParticle(Particle particle, EmitterShape emitterShape) {
        emitterShape.getRandomPoint(particle.position);
        this.applyVelocityVariation(particle);
    }
The velocity's variation of the particles.
jme3-core/src/main/java/com/jme3/effect/influencers/DefaultParticleInfluencer.java