Table 1: Dominant excitation and damping mechanisms for the smallest grains considered (  Å), as a function of idealized environment (see definitions in Table 1 of [7]). Two or more mechanisms are written down if they are of comparable importance, by decreasing order of importance. “e.d” stands for electric dipole radiation torque.

Phase DC MC RN PDR

Excitation coll. (neutrals, ions) coll. (ions) IR coll. (neutrals)
Damping e.d., coll. (neutrals) plasma drag e.d., IR e.d., IR, coll. (neutrals)

Phase CNM WNM WIM

Excitation coll. (ions, neutrals) coll. (ions, neutrals), IR coll. (ions)
Damping e.d. e.d e.d