A NEW STUDY OF THE COSMIC RAY DIURNAL VARIATION IN RELATION TO GEOMAGNETIC ACTIVITY

A comparison is being made between three ways of grouping the days according to their K/sup p/ indices. The cosmic ray diurnal variation on the most dirturbed days is seriously affected by U.T. variations, the latter sometimes obliterating the true diurnal variation. Major phase shifts, not correlated with geomagnetic activity, are also a disturbing factor, although of less importance. The phase of the diurnal variation decreases with increasing geomagnetic activity. This is in accordance with an explanation offered in previous papers. (auth)