Newly Digitized Data From Scandinavian Magnetometer Array Network Shows Large Regional Differences in Magnetic Environment

The International Magnetospheric Study (IMS) took place from 1977 to 1979. An objective was to study the magnetosphere at different heights on the Earth and in space simultaneously. The Scandinavian Magnetometer Array (SMA), where a dense magnetometer array was placed in the northern part of Scandinavia, was part of the IMS. This array extended 1,570 km in north-south and 1,290 km in east-west directions. The SMA-magnetometers contained a camera with 35 mm film and three wire-suspended magnets. These instruments recorded the movement of the magnets optically on the film. The usability of the SMA data has been limited by time-consuming digitization by hand. Thus, most of the recordings has been left nondigitized and unstudied. We have developed a method, named DigiMAG, to digitize the SMA recordings by using a custom-built device. This article presents the high-latitude dynamics of the strongest magnetic storm in 1977 between October 26 and 30. We analyze newly digitized data from Rostadalen (ROS), Evenes (EVE), Ritsemjokk (RIJ), and Kiruna (KIR) stations for the three storm-time substorms on October 26-29, 1977. The results show that in the vicinity of the 65 degrees latitude, the storm-time differences of horizontal magnetic components can exceed 500 nT. During the recovery phase of a substorm, 2.8 nT km(-1) difference arises over a distance of 167 km between the H-component time derivatives of ROS and RIJ stations in 3 minutes.