  Within the frames of Alfv\'en sweep maser theory the description of
morphological features of geomagnetic pulsations in the ionosphere with
frequencies (0.1-10 Hz) in the vicinity of Schumann resonance (7.83 Hz) is
obtained. It is shown that the related regular spectral shapes of geomagnetic
pulsations in the ionosphere determined by "viscosity" and "elasticity" of
magneto-plasma medium that control the nonlinear relaxation of energy and
deviation of Alfv\'en wave energy around its equilibrium value. Due to the fact
that the frequency bands of Alfv\'{e}n maser resonant structures practically
coincide with the frequency band delta- and partially theta-rhythms of human
brain, the problem of degree of possible impact of electromagnetic "pearl" type
resonant structures (0.1-5 Hz) onto the brain bio-rhythms stability is
discussed.
