Figure 3: Emissivity per from irregular grains of different degrees of irregularity with and K in the WIM for the case in which the electric dipole moment is isotropically oriented in the grain body (i.e., case 1 with ). The emission spectrum shifts to higher frequency as decreases (i.e., grain becomes more irregular). Here, the grain mass is held fixed as changes. The figure is reproduced from Hoang et al. .