Letter | Published:

# Dependence on Latitude of the Amplitude of the Diurnal Variation of Cosmic Rays

## Abstract

THE solar diurnal variation of cosmic-ray intensity is usually assumed to be due to the rotation of the Earth in a cloud of particles. The velocity of the latter should be randomly distributed with a small additional component in one direction, thus constituting a kind of particle wind. For various reasons it can be assumed that this wind is following the Earth, approximately parallel to its orbital plane1. The yearly mean amplitude of the diurnal variation should then have a maximum for primary particles having asymptotic directions approximately parallel to the equatorial plane. It should have a minimum for primaries with asymptotic directions parallel to the Earth's axis of rotation. For an experimental study of the relative magnitude of the amplitudes in these directions, it is necessary to record the variations of cosmic-ray intensity with inclined counter telescopes. However, it is difficult to gain access to both directions at one and the same point on the Earth's surface.

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## References

1. 1

Sandström, A. E., Tellus, 8, 18 (1956).

2. 2

Brunberg, E. Å., Tellus, 5, 135 (1953); 8, 215 (1956).

3. 3

Sandström, A. E., Kosmos, 33, 56 (1955) (in Swedish).

4. 4

Brunberg, E. Å., and Dattner, A., Tellus, 6, 73 (1954).

5. 5

Brunberg, E. Å., Ark. Fys., 14, 195 (1958).

6. 6

Elliot, H., and Rothwell, P., Phil. Mag., 1, 669 (1959).

7. 7

Stensland, B., Ark. Fys., 11, 253 (1957).

8. 8

Discussion on pp. 402–403, “Electromagnetic Phenomena in Cosmical Physics”, edit. by Lehnert, B. (Cambridge, 1956).