Fine structure of air shower cores observed with a spark chamber at 5 200-m altitude

Spark chambers forming a 5-m2 array have been operated at the center of the Chacaltaya air shower array in Bolivia at an altitude of 5 200 m. Double-cored showers and steep-cored showers are observed, and a comparison is made with observations at sea level. The location of the electromagnetic core is compared with that of the nucleonic core.