Links of Terrestrial Volcanic Eruptions to Solar Activity and Solar Magnetic Field
We compare frequencies of volcanic eruptions (VEs) in the past 270 years with variations of solar activity and summary curve of eigen vectors (EVs) of the solar background magnetic field (SBMF) from the WSO synoptic magnetic maps. In the period 1868 – 1950 and 1990-2020 the total numbers of volcanic eruptions are maximal during the maxima or the descending phase of the magnetic field cycles with the dominant southern polarity, and minimal during the maxima or ascending phase of the magnetic field cycles with the northern polarity. While in the earlier years (1762-1868) this link disappeared. The frequency analysis of VEs with Morlet wavelet reveals the dominant period of about 22 years and weaker periods of 10.7 and 55-70 years. Comparison of VE frequencies with the modulus summary curve (MSC) of EVs of SBMF for solar cycles after 1868 reveals a strong positive correlation (coefficient of 0.84) with the maxima of VEs occurring when the summary curve of EVs derived from the solar magnetic fields have the southern polarity, or more active southern hemisphere of the Sun, and minima when the northern one. The maxima of VE frequencies associated with southern polarity of the summary curve of EVs can be linked with the increased disturbances in the geomagnetic field leading to increased volcanic activity. The correlation between VEs and MSC cycles before 1868 becomes much lower and negative (coefficient -0.33) that can reflect a real change caused by migration of the Earth’s magnetic pole to lower latitudes. The next maximum of VEs is expected during cycle 26 when the EVs have the southern polarity that can affect the terrestrial atmosphere transparency and solar radiation input to Earth during the modern Grand Solar Minimum (2020-2053).
