  The interaction between two co-propagating electromagnetic pulses in a
magnetized plasma is considered, from first principles, relying on a
fluid-Maxwell model. Two circularly polarized wavepackets by same group
velocities are considered, characterized by opposite circular polarization, to
be identified as left-hand- or right hand circularly polarized (i.e. LCP or
RCP, respectively). A multiscale perturbative technique is adopted, leading to
a pair of coupled nonlinear Schrodinger-type (NLS) equations for the modulated
amplitudes of the respective vector potentials associated with the two pulses.
Systematic analysis reveals the existence, in certain frequency bands, of three
different types of vector soliton modes: an LCP-bright/RCP-bright coupled
soliton pair state, an LCP bright/RCP-dark soliton pair, and an
LCP-dark/RCP-bright soliton pair. The value of the magnetic field plays a
critical role since it determines the type of vector solitons that may occur in
certain frequency bands and, on the other hand, it affects the width of those
frequency bands that are characterized by a specific type of vector soliton
(type). The magnetic field (strength) thus arises as an order parameter,
affecting the existence conditions of each type of solution (in the form of an
envelope soliton pair). An exhaustive parametric investigation is presented in
terms of frequency bands and in a wide range of magnetic field (strength)
values, leading to results that may be applicable in beam-plasma interaction
scenarios as well as in space plasmas and in the ionosphere.
