What are the smallest lava fragments produced by an explosive eruption called?

Tiniest fragments of lava obtained by  explosion is termed as volcanic ash

Explanation:

Tiniest fragments of lava obtained by  explosion is termed as volcanic ash

Volcanic ash is a combination of fragments of stone, mineral and glass released during a volcano eruption. The molecules are quite small— in size fewer than 2 millimeters. The particles which constitutes volcanic ash can actually travel long distance through wind, due to their small size and low density.

radiative zone

explanation    

radiative zone is the layer of the sun which energy is transferred away from the core by radiation. although, the core is the only part of the sun that produces an appreciable amount of heat through fusion. in fact, 99% of the energy produced by the sun takes place within 24% of the sun's radius.