  The visible diameter of Sun oscilates with a period of 160 min. The same type
of periodicity is also found in a huge number of solar radiation parameters. To
elucidate the origin of these longitudinal radial pulsations we have used the
equation for the equilibrium of inner layers which, after linearization, turned
into the harmonic oscilator equation. The latter equation allows radial
pulsations whose period and wave length were calculated using regresion
expresions for the gas presure and density in various layers. The radial
pulsations originate at the surface of active zone and propagate til the
litosphere, where they undergo full inner reflection producing undersurface
stationary waves with a period of 150-160 min.
