A fresh supply of yellow froth (probably the same type of elemental sulfur found in the "cool acid-brine" crater lake at Kawa Ijen) is brought up by the plume and pushed out toward the crater wall.
Microwave Plasma Thruster (MPT) is a new type of electro-thermal thruster, which has widely applied prospect because of its high specific impulse, long lifetime, low plume contaminant and so on.