1 A specific form of aurora that consists of a folded, ribbon-like structure, and frequently associated with auroral rays. A band often develops from an auroral arc as the display intensifies, and multiple bands are commonly seen. Often known as an auroral curtain.
2 A form of noctilucent cloud (classified as Type II), consisting of long streaks of cloud of a generally fibrous structure. A common form, often observed simultaneously with billows (2).