1. This paper forms a sequel to one entitled “An Outline of a Theory of Magnetic Storms,” published several years ago. In that paper I determined the average
additional
variations in the three components of the earth's magnetic field (for observatories in magnetic latitudes up to about 60°N.) which during times of considerable magnetic disturbance—commonly called magnetic storms —are superposed on the normal variations. The storms dealt with were such as had a commencement sufficiently definite for its epoch to be estimated to within an hour. The average additional variations of the field were shown to be separable into two parts, one depending on “storm-time” (that is, time reckoned from the commencement of the storm), and the other being a “diurnal” variation depending on local time. Besides these average variations there are, of course, less regular features peculiar to each individual storm.
On certain average characteristics of world wide magnetic disturbance