Differences in diurnal variation of vertical magnetic intensity in Southern California

This paper sets forth the results of an experimental investigation of the diurnal variation in the intensity of the vertical component of the Earth's magnetic field in the northern half of Southern California. It also presents a discussion of the effect which the diurnal variation may have on the results of magnetic investigations of geologic features in this region. Attention was directed primarily to determining to what degree the diurnal variation is or is not constant over the various areas of the region regardless of the local weather prevailing at the different localities. Southern California is divided into local topographic areas characterized by diverse atmospheric conditions. Areas open to oceanic breezes are frequently covered with fog and are consequently cool in summer; other districts closed to the sea by ridges may receive simultaneously extreme amounts of solar energy directly from the Sun, or may become heated by foehn or valley winds from adjacent regions. These variable local conditions of energy‐absorption and radiation may influence earth‐currents if they are considered as induced currents circulating in conductive paths in the Earth's crust. Any change in earth‐currents would influence magnetic intensities by the amount of change in magnetic flux produced by the disturbed earth‐currents.