  Debris disks often take the form of eccentric rings with azimuthal
asymmetries in surface brightness. Such disks are often described as showing
"pericenter glow", an enhancement of the disk brightness in regions nearest the
central star. At long wavelengths, however, the disk apocenters should appear
brighter than their pericenters: in the long wavelength limit, we find the
apocenter/pericenter flux ratio scales as 1+e for disk eccentricity e. We
produce new models of this "apocenter glow" to explore its causes and
wavelength dependence and study its potential as a probe of dust grain
properties. Based on our models, we argue that several far-infrared and
(sub)millimeter images of the Fomalhaut and epsilon Eridani debris rings
obtained with Herschel, JCMT, SHARC II, ALMA, and ATCA should be reinterpreted
as suggestions or examples of apocenter glow. This reinterpretation yields new
constraints on the disks' dust grain properties and size distributions.
