Researchers from the University of Warwick and the British Antarctic Survey have found that large-scale magnetic storms, which can cause disruptions to power grids and communications, occur on average every 25 years. The researchers wrote about this in Geophysical Research Letters.
“These superstorms are quite rare events, but assessing their likelihood is an important part of planning measures to protect national infrastructure,” said Sandra Chapman, a researcher at the Center for Fusion, Space and Astrophysics at the University of Warwick. "This study offers a new method for analyzing historical data to better understand the overall picture of the likelihood of superstorms and predict their activity in the foreseeable future."
Space weather is determined by the activity of the sun. Faint magnetic storms usually occur, but occasionally larger electromagnetic events occur that can have a significant impact on the inhabitants of the Earth and human electronics. One way to monitor this space weather is by observing changes in the magnetic field on the Earth's surface.
Since the dawn of the space age, high quality observations have been available at several stations. The sun has an approximately 11-year cycle of activity, during which its intensity varies. But the data available to researchers covers only five cycles of solar activity - not that much. Therefore, the authors of the new work used to analyze the value of the geomagnetic activity index over the past 150 years - this is already 14 solar cycles.
Using the highest annual aa for the entire observed period, the researchers found that a typical superstorm occurred in 42 out of 150 years (28%), while the “strongest” superstorm occurred in 6 out of 150 years (4%) or one every 25 years. To date, the most powerful of all recorded by man is considered a magnetic storm in 1989, which caused a major power outage in Quebec.