Cosmic-Ray Characteristic Parameters for Yangbajing (Tibet) Experiments

The geomagnetic shielding imposed on the charged particle access to the Yangba jing measurement site is discussed. The Rc time dependence on the McIlwain's parameter resulted to be the same found in the past by Shea et al. (1987). Moreover, huge geomagnetic perturbations change the rigidity threshold of the cosmic ray incoming even at this Tibetan location.