Secular variations on the North American tectonic plate

Abstract

Based on the results of geomagnetic observatories located near the North magnetic pole and in the middle latitudes of the North American tectonic plate, the secular variations (SV) of the Earth’s geomagnetic field have been studied. The influence of solar activity on SV on the North American plate has been shown. The author has identified the SV source of non-dipole origin with a period of about 22 years. The source did not affect SV in the XX—XXI cycle of solar activity probably due to the influence of the SV jerk, but it showed itself well in the XXII—XXIV cycles of solar activity. It is demonstrated that the influence of the SV source increases with increasing latitude of the observatory and is almost imperceptible at low latitudes. According to the Minuk observatory and others, a 100-year cycle of age-related variation has been identified — the early 20th century: a maximum took place in the 1960s and cycle termination was in 2013. Following the observatories located on the eastern part of the plate, the SV acceleration triggered by the influence of the Atlantic focus has been calculated. The research identifies that the «activation» of the SV Atlantic focus occurs with an expansion in the number of recurrent geomagnetic storms, which is evidenced in odd cycles of solar activity (the VMS direction from the Sun). According to observatories located near the Pacific Plate (west coast of North America), the impact of the Atlantic focus on SV is not as pronounced as in the eastern part. However, there is an influence of the non-dipole SV source depending on the observatory’s latitude and solar activity.