Disable actor gravity

I have a class which derives from actor. In this class I have 2 object - one UStaticMeshComponent and the other is fireBallParticle. I want to disable this actor’s gravity. I have been tried to user SetEnableGravity(false) for both components but it doesn’t work:

AFireBall::AFireBall(const FObjectInitializer& ObjectInitializer)
	PrimaryActorTick.bCanEverTick = true;

	mesh = ObjectInitializer.CreateDefaultSubobject<UStaticMeshComponent>(this, TEXT("Mesh Component"));
	RootComponent = mesh;

	fireBallParticle = ObjectInitializer.CreateDefaultSubobject<UParticleSystemComponent>(this, TEXT("fireBallParticle"));

How can I disable the gravity?