The Geographic Incidence of Aurora and Magnetic Disturbance, Northern Hemisphere

Fritz [see 7 of "References" at end of paper] in a famous memoir published in 1881 discussed the frequency and characteristics of aurora observed in the Northern Hemisphere during the years 1700 to 1872. Using observations during this 172-year period [8] he also constructed his well-known map of isochasms of equal auroral frequency. Beginning is made here in the statistical analysis of the auroral data since accumulated, a task of considerable magnitude if undertaken with any pretense at completeness. The present paper is concerned mainly with the variation with geographic position of the average daily frequency of aurora in high latitudes, and of geomagnetic disturbance. Since 1872 much observational material has accumulated but there