The Latitude and Longitude Effects in Cosmic Rays Over the United States and Canada at 30,000 Feet

The change with geomagnetic latitude of the ionizing particles at 310 g/cm^-2 atmospheric pressure (30,000 ft.) that could penetrate various thicknesses of absorber was measured by Biehl, Neher, and Roesch [1] over a range of latitude of 64° geomagnetic north to the geomagnetic equator along latitude 80°W. These flights show that most of the latitude effect is over at 50° as one proceeds north and this was independent of the absorber used or whether the total radiation at that altitude was measured or only that near the vertical. On the other hand, Swann, Morris and Seymour [2] find a 10 percent increase for a 10° increase in geomagnetic latitude at 30,000 feet even beyond the "knee" of the curve. Although no mention of an absorber was made, presumably their measurements were made with a lead absorber. number of flights having a further bearing on this point have recently been made, covering the latitude range particularly from 40° to 64° geomagnetic north with counter telescopes and ionization chambers, the latter both unshielded and shielded with 10 cm of lead.