circular orbits (“suspension" orbits) was confirmed. [@Stahl-etal-12] studied the halt and “levitation" of particles at the corresponding “Eddington sphere" and discussed its implications for accretion onto a luminous star. In accord with intuition and experience, they concluded that the effective cross section of such a shining source is typically less than the geometric value, because the infall onto the star’s surface is prevented by outgoing radiation. In contrast, [@OhPK-13] inferred from numerical experiments that luminosity [*enhances*]{} the effective cross section of a relativistic centre about 4 times. [@Stahl-KWA-13] and [@MishraK-14] analyzed the response of the matter suspended on the equilibrium “Eddington sphere" on a sudden luminosity change, mainly aiming at determination of conditions under which ejection from the system may occur.

In the present paper, we consider a radiative flux directed away from the equatorial plane in the “vertical" direction, in an effort to model the situation which may be generated by a thin accretion disc surrounding a compact gravitational object. We investigate the behavior of test particles above the disc, mainly in the region near the axis of symmetry. This question has already been tackled several times in the literature in connection with the acceleration/deceleration and axial collimation of 