A Monte Carlo calculation of the nucleonic cascade in the atmosphere has been carried out. Preliminary results are presented and compared with measurements of the secondary proton spectrum at sea level.

An analogue method for determination of electron orbits in a magnetic dipole field has been developed by Malmfors several years ago. The method is in principle a scale model experiment in a vacuum chamber where the results are obtained by measuring the deflection of an electron beam in the field of a “terrella”. During the last years this method has been further developed, and particle orbits corresponding to the following momenta have now been measured: 2 · 109 — 1010 eV/cOrbits arriving at magnetic latitude 58° in E, S, W and N directions at zenith angles of 0°, 20°, 40°, 60°, 80°. Orbits arriving from zenith at different latitudes beginning with 38° and continuing at intervals of 2 degrees up to the pole. 1010 — ∞ eV/cOrbits arriving at magnetic latitude0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, and 90° from E, S, W and N directions at zenith angles of 0°, 8°, 16°, 24°, 32°, 40°, 48°, 56°, 64°, 72°, and 80°. The direction of orbits far away from the dipole is published as a function of momentum. The particles are assumed to move towards the earth and to be positively charged. This article includes only diagrams for the latitudes 90°—60°. The remaining ones will be published in the next issue of this journal.

In the preceding issue of Tellus were pub- lished the first results of our investigations of cosmic ray orbits in the field of a magnetic dipole. The investigations were carried out by measurements o n a model with particle mo- mentum range corresponding to 1010-eV/c. A detailed description of the apparatus and the performance of the experiment is given in part I of the present paper.

The recorded data of diurnal variation of the cosmic ray intensity are analysed. By using the known deflection of the cosmic ray particles in the geomagnetic field (Brunberg and Dattner 1953) and under an assumption of an anisotropy in the primary cosmic radiation, it is shown that the momentum of the primary radiation and the direction of the anisotropy can be determined. The anisotropy is explained as an effect due to the distribution of cosmic ray particles rotating with the solar magnetic field as suggested by H. Alfvén. The diurnal variation is ascribed to the earth's rotation in the anisotropic distribution of cosmic ray particles. The theoretical amplitude of this variation is calculated.

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