How can i access to the property of two nested particle system ?

Hi all,

i just started with Unity.

i have created a nested particle system, so structured:

and import it by this code: public var PS_SparkBraking:ParticleSystem;

i want to change by code any parameters like: StartSpeed , startSize on every particle system .

i tried access by 'GetComponent' or 'GetComponentsInChildren' but dosn't work !

How can i do ?

thanks