The heat from the bonfire is transferred to the student's hands mainly, but not exclusively, through the process of RADIATION.
There are three mechanisms or processes of heat transfer: conduction, convection, and ratiation.
Conduction is carreid out by contact; it requires that the two objects are touching each other. This is not the case.
Convection is the heat transferred by the movement of the fluids (liquids ang gases). In some extent this happens in this case, but it is not the dominant effect becasue air is not a very good conductor. Specially if there is not much air movement (wind).
Thermal radiation is carried out by electromagnetic waves. When there is a source of intense heat, like the fire, the heat is propagated by radiation.
Then really, the heat from the bonfire gets to the student's hands by convection and radiation, but as fire is very intense (its temperature is very high), and as long as the air is calmed, the dominant process is radiation. If there is wind, convection starts to be important.
