Q:

Film about pieces of the sun tracking people thermally and incinerate them

The movie I want to find is about pieces of the sun that come down to Earth and they sense heat, like the pieces see thermally, and if a human touches them they get instantly incinerated. It’s been a while, like 8 years, since I’ve seen it. I just want to re-watch it.

A:

I’m pretty certain you’re thinking of The Darkest Hour.
Not pieces of the sun but some kind of alien race invading earth.

Young entrepreneurs Sean (Emile Hirsch) and Ben (Max Minghella) meet stranded travelers Natalie (Olivia Thirlby) and Anne (Rachael Taylor) at a hot Moscow nightclub. Their whole world changes in an instant when an alien attack devastates the city and everything goes dark. Joined by a Swedish businessman (Joel Kinnaman), the youths emerge from hiding days later and must somehow fight back against a nearly invisible enemy that could find and disintegrate them at any moment.
Google reviews

In the trailer, you can see the cop touching the light with the nightstick and turning to dust, as OP said (it’s like 40 seconds in):

