The Daily Variation of the Cosmic Ray Nucleonic Component at Murchison Bay and Uppsala

Abstract

In both places the monitors were of the standard pattern with 12 proportional counters filled with 97 per cent enriched B10F8. The first and second harmonics of the mean daily variation have been determined both for yearly periods and for each sun rotation period. Vector sum diagrams for the first harmonics in the latter case are given covering the intervals 31 Aug. 1956 to 15 Aug. 1959 for Uppsala and 13 Sept. 1957 to 29 April 1959 for Murchison Bay. In some instances a considerable phase shift has taken place from one sequence of sun rotation periods to another. These phase shifts were not contemporary at the two stations. The first harmonic of the 12-month means displays a high degree of constancy with only a small secular phase shift. The amplitudes of the second harmonics are very small. Conditions are especially favourable concerning the deviation in the earth’s magnetic field of the particles registered by the Murchison Bay monitor. Accordingly it has been possible to determine the direction of the anisotropy with a fairly good accuracy. The Murchison Bay records do not show any prominent phase shift with the Kp index. Concerning Uppsala, days with [Kp]max ≤ 1+ have a later time of maximum than other days. The influence of single days with an abnormal daily variation is discussed.