The nature of the B-(3) field

The nature of the B-(3) field is determined through deductions from its mat hematical definition; B-(3) is a vector function of the magnetic field of e lectromagnetic radiation. The sign and magnitude of B-(3) measure the polar ization of the radiation, and it is re-normalized to define the Polarizatio n Index (a dimensionless number of magnitude unity), which proves to be ide ntical with one of Stokes's parameters. This is revealed to be the essentia l nature of the B-(3) field. The definition of B-(3) (and of the Polarizati on Index) is generalized in terms of all components of the electromagnetic field rather than only the transverse magnetic components. The analysis leads to internal inconsistencies if the B-(3) field is presum ed to be the longitudinal component of the physical magnetic field of elect romagnetic radiation as asserted by M.W. Evans (the originator of the theor y of the B-(3) field). This inference explains the failure of experimental investigations to detect the hypothetical longitudinal magnetic field of ra diation. It also corroborates a disproof by counter-example by E. Comay; (C ) 1999 Elsevier Science B.V. All rights reserved.