  In this paper global surface wave modes supported by plasma discontinuities
at both the magnetopause and the plasmapause are considered. The ionosphere at
the ends of the magnetic field lines of the earth outer magnetosphere is
considered as reflecting boundaries of the surface waves that propagate along
the plasma boundaries. As a result a standing wave structure along the magnetic
field fluxes of the outer magnetosphere, i.e. surface wave resonance structure
can be formed. Due to quantized wavenumbers along the magnetic field lines, the
surface wave resonance possesses quantified frequencies in a following way: f =
nfres, where fres is frequency of the corresponding fundamental surface wave
resonance and n is an integer. Global Pc5 pulsations have been observed and
interpreted mostly as cavity modes of the earth magnetosphere. The global Pc5
pulsations however could alternatively be interpreted as ultra low-frequency
surface wave resonances of the earth magnetosphere that do not necessarily
involve the cavity mode-field aligned resonance transformation concept.
