Modeling of the southern magnetic arm of NGC 4254 by stretching/shearing and
compression processes. The radio properties of the N magnetic arm are
regarded as the initial conditions for the S magnetic arm (region 3 and 1 in
Table 2, respectively). The compression and stretching factors were
adjusted so as to yield the observational values (given in italics) of
synchrotron emissivity ratio S2/S2 or the degree of polarization in
the southern arm p2 (see Sect. 3.4).