Chirality, helicity and the rotational content of electromagnetic fields

Publication date: Available online 2 July 2019Source: Physics Letters AAuthor(s): M. Fernández GuastiAbstractThe chirality continuity equation in the presence of charge and current is obtained from the complementary fields formalism. In the presence of sources, it is strongly suggested that the chirality should be defined proportional to με(H⋅∂tE−E⋅∂tH) instead of the usual definition H⋅(∇×B)+εE⋅(∇×E). Both definitions are equivalent for free fields. The relationship between helicity ϱAC and chirality ϱEH for arbitrary wave solutions is shown to be ∂t2ϱAC=με(1εϱEH+A⋅∂t2B−C⋅∂t2E). The helicity continuity equation can be transformed into the chirality scheme via a time derivative transformation of all the field functions. Following a mechanical analogue, the helicity flow is shown to be equivalent to the angular momentum Jrp=r×p, while the chirality flow is equivalent to JvF≡r˙×p˙. Both quantities are shown to adequately describe the rotational content of the electromagnetic field.

Source: Physics Letters A - July 3, 2019 Category: Physics Source Type: research