Version: 2019.1
public ParticleSystem.ExternalForcesModule externalForces ;

Description

Script interface for the Particle System external forces module.

This module enables ParticleSystemForceField and WindZone components to affect the Particle System.

Particle System modules do not need to be reassigned back to the system; they are interfaces and not independent objects.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour { void Start() { ParticleSystem ps = GetComponent<ParticleSystem>(); var ex = ps.externalForces; ex.enabled = true; ex.multiplier = 0.1f; } }