Geomagnetic conditions are analyzed when carrying out measurements at the Campinas balloon shoting-range in the region of the Brazilian magnetic anomaly. It is shown that in the region takes place gradual lowering in time of the L shells. The conclusion is made on the radial particle diffusion as the most probable cause of observed in the region particle precipitation in the upper layers of atmosphere. An instrument is described for balloon investigations of particle precipitations. The instrument permits to determine the kind of the particles and to measure their energy. Preliminary results of measurements of the hight dependences of secondary electrons and protons are presented. 6 refs.; 7 figs.; 2 tabs.