How to create a fire particle system on sphere?

I am trying to add a particle system to sphere. I want fire follows the sphere in natural way:

 1. When sphere is falling from top to bottom the fire tail should be upwards.
 2. and when sphere goes upwards fire tail must be facing bottom as shown in following 2 images

How to create fire particle system in easy way? Is there any free assets to do it quickly?
Please help. Thanks in advance.

In the main module of the particle system set the Simulation Space to World. Then tweak the emission and lifetime settings until you get a good effect. You’ll probably want to look at the Size Over Lifetime module a well.

You might also consider using the Trails module of the particle system.