Cassini and extra force constraints to nonminimally coupled gravity with a screening mechanism

We consider a nonminimally coupled curvature-matter gravity theory at the Solar System scale. Both a fifth force of Yukawa type and a further non-Newtonian extra force that arises from the nonminimal coupling are present in the solar interior and in the solar atmosphere up to interplanetary space. The extra force depends on the spatial gradient of space-time curvature R. The conditions under which the effects of such forces can be screened by the chameleon mechanism and be made consistent with Cassini measurement of parametrized post-Newtonian parameter gamma are examined. Constraints from spectroscopic observations of the solar atmosphere are also taken into account. This consistency analysis requires a specific study of the Sun's dynamical contribution to the arising forces at all its layers.