  Based on the results of applying the extended ADC emission model for low mass
X-ray binaries to three Z-track sources: GX340+0, GX5-1 and CygX-2, we propose
an explanation of the CygnusX-2 like Z-track sources. The Normal Branch is
dominated by the increasing radiation pressure of the neutron star caused by a
mass accretion rate that increases between the soft apex and the hard apex. The
radiation pressure continues to increase on the Horizontal Branch becoming
several times super-Eddington. We suggest that this disrupts the inner
accretion disk and that part of the accretion flow is diverted vertically
forming jets which are detected by their radio emission on this part of the
Z-track. We thus propose that high radiation pressure is the necessary
condition for the launching of jets. On the Flaring Branch there is a large
increase in the neutron star blackbody luminosity at constant mass accretion
rate indicating an additional energy source on the neutron star. We find that
there is good agreement between the mass accretion rate per unit emitting area
of the neutron star mdot at the onset of flaring and the theoretical critical
value at which burning becomes unstable. We thus propose that flaring in the
CygnusX-2 like sources consists of unstable nuclear burning. Correlation of
measurements of kilohertz QPO frequencies in all three sources with spectral
fitting results leads to the proposal that the upper kHz QPO is an oscillation
always taking place at the inner accretion disk edge, the radius of which
increases due to disruption of the disk by the high radiation pressure of the
neutron star.
