Fig. 1.
Schematic illustration of photophoretic forces. A and B show, respectively, thermal gradient (ΔT) and accommodation coefficient (Δα) forces acting on idealized spherical particles. Note that for ΔT, the photophoretic force (Fp) is aligned with the asymmetry in the radiation field that drives the thermal gradient, in this case the incident solar radiation (insolation); whereas for Δα, the vector is oriented along the asymmetry in the accommodation coefficients and rotates with the particle. C illustrates design of the disk described in the text, whereas D illustrates the fields and forces acting on the disk as described in SI Text.