Scripting Reference
Component.particleEmitter

var particleEmitter : ParticleEmitter

Description

The ParticleEmitter attached to this GameObject (null if there is none attached).

JavaScript 
    particleEmitter.emit = true;
using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        particleEmitter.emit = true;
    }
}
import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        particleEmitter.emit = true