Astronomers have improved the sunspot catalog

The sun is a large, incandescent ball of boiling gas, heated so much that electrons are torn away from atoms, forming a plasma – a circulating mixture of charged particles. Due to the movement of these charges, the Sun has the strongest magnetic field. Dark areas on the surface of the Sun – sunspots – are places where the magnetic field, as it were, “burst out” to the surface. The incidence of sunspots varies according to the solar cycle, which lasts an average of 11 years.

At the beginning of the cycle, there are almost no spots, but as the cycle develops, they more and more often appear first in the mid-latitude region, from where they move to the equator. As the equator of the Sun rotates faster than the poles, the star’s magnetic field becomes entangled, amplified locally and exits through the photosphere in the form of loops, which capture plasma with them and eject it into space. Huge clouds of plasma burst from the surface of the Sun into space at high speed. If the ejection is directed towards the Earth, magnetic storms can occur, which can damage equipment on satellites, interrupt radio transmissions and even disable ground-based power systems. Therefore, observation of sunspots is of great importance for predicting dangerous phenomena in space weather.

Sunspots are now monitored by about 80 observatories around the world, and their findings are collected at the SILSO World Data Center at the Royal Observatory of Belgium. Although the total number of sunspots has been systematically monitored since the 18th century, recent models indicate that a deeper understanding of solar activity is possible by taking into account the dynamics of sunspots in each hemisphere separately. And much less such data has been accumulated: the most important catalog of solar activity provides data on the Wolf’s hemispheric numbers (numbers reflecting the number of sunspots) only since 1992.

Researchers from the University of Graz, the Kanzelhohe Observatory, Skoltech and the SILSO World Data Center have come up with a way to dramatically expand the available data sample by reconstructing the historical sunspot population by hemisphere. As the authors write in Astronomy & Astrophysics, the reconstruction is in good agreement with the existing hemispheric data, and taking into account the dynamics of the number of sunspots in each hemisphere separately actually allows more accurate predictions of the solar cycle. Updated catalog presented on the website of the World Data Center for the Observation, Conservation and Propagation of International Wolf Numbers (WDC-SILSO).

Based on materials from Skoltech.

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