An electrodeless discharge lamp includes an electrodeless lamp bulb enclosing a fill which emits light when excited, an excitation structure positioned near the bulb and adapted to excite the fill, a rotation assembly connected to the bulb and adapted to rotate the bulb during operation of the lamp, and a plurality of structures formed on an outer surface of the bulb adapted to enhance cooling of the bulb. In some cases the structures are distributed in accordance with a temperature profile of the bulb to provide a relatively more uniform bulb temperature during operation. Some structures include protrusions which are distributed around the entire surface of the bulb. Some structures include protrusions which are distributed around the entire surface of the bulb except in the region of the bulb equator. Some structures include a plurality of ribs attached to an outer surface of the bulb, wherein the ribs are aligned transverse to a plane of the equator of the bulb. In some cases the ribs are offset from the surface of the bulb by one or more supports. Some structures include a pair of rings attached to an outer surface of the bulb.
 Certain inventions described herein were made with Government support under Contract No. DE-FC26-00NT40988 awarded by the Department of Energy. The Government has certain rights in those inventions.