The normality of geomagnetic disturbance at Huancayo

Summary Evidence is adduced indicating that geomagnetic disturbance at Huancayo isnormal, that is, comparable with that shown elsewhere in similar latitudes —as contrasted with the remarkable Huancayoabnormality, in the horizontal magnetic force, of the quiet-day solar and lunar daily variations, and in theS _q augmentation (solar flare effect). the normality of magnetic disturbance at Huancayo is manifested by the disturbance daily variationS _D, and by the storm-effectD _st and its associated changes of daily mean (D _m) and the non-cyclic variation; it is not stated whether or not the irregular part,D _i, is normal. The normality ofD _st seems natural according to theChapman-Ferraro theory of magnetic storms, but the normality ofS _D is less easy to explain.Prof.Sydney Chapman, Research Associate, California Institute of Technology, under Signal Corps Project No. 24-172 B; on leave (from April 1950 to March 1951) from Oxford University, Queen's College,Oxford, England.