Mathematical research of sunspots

Summary: Sunspots have long been observed and mathematicians and scientists continue to try to understand them and their effects.

Sunspots are a not yet fully explained phenomenon tied to solar activity. The sun is Earth’s richest source of heat and light. Furious eruptions of energy take place on the surface of the sun. In the core, nuclear reactions occur because of the immense temperature and pressure. Through a process known as “convection,” millions of tons of hydrogen are converted into helium every second and are then expelled at the surface of the sun as light and heat. Sunspots have a magnetic field strength that is thousands of times stronger than Earth’s magnetic field. These magnetic fields inhibit convection to create relatively cooler areas, which appear as dark spots on the surface of the sun. Scientists and mathematicians have long attempted to understand their behavior and oscillations and have used mathematical tools like differential equations, hexagonal planforms, and time series analyses. They also count the number of sunspots and examine possible relationships between this number and factors on Earth, like radio disruptions, land temperature, and weather phenomena.

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History

Direct observation of the sun is very dangerous, which historically made sunspots hard to study and quantify. In ancient times, Chinese astronomers recorded solar activity. Mathematician and astronomer Thomas Harriot, noted for his work on algebra, is also credited as the discoverer of sunspots. Increased understanding of the nature of sunspots, including the observation that they often occurred in groups and that they moved relative to one another as the sun rotated, is tied to the development of the telescope in the seventeenth century. One of Galileo Galilei’s works on sunspots offered evidence for the heliocentric system of Nicolaus Copernicus, and this led to debate about sunspots, as evidenced in astronomer, mathematician, and Jesuit Christoph Scheiner’s views and works.

In the eighteenth century, Alexander Wilson used a geometric argument to show that sunspots were depressions. In the nineteenth century, pharmacist and amateur astronomer Heinrich Schwabe collected data on the periodicity of sunspots. Systematic observations, such as the approximately 11-year cycle, were made by Rudolph Wolf starting in 1848, who also measured the number of sunspots present on the surface of the sun. Wolf was primarily an astronomer but he also taught mathematics and physics. His observations were disputed by other astronomers, but his methods, which were based on statistical analyses, were eventually accepted as correct. Wolf’s formula continues to be used in the twenty-first century as one of the sunspot indices. The International Sunspot Number is compiled worldwide by the Solar Influences Data Analysis Center in Belgium and by the U.S. National Oceanic and Atmospheric Administration. In the twenty-first century, sunspots are observed with solar telescopes, which use various filters, and specialized tools such as spectroscopes and spectrohelioscopes. Amateurs generally observe sunspots using projected images.

Waxing and Waning

Scientists know that the sun had a period of relative inactivity in the seventeenth century, which corresponds to a climatic period called the “Little Ice Age.” Evidence suggests that similar periods existed in the distant past, which means there might be a connection between solar activity and terrestrial climate. The magnetic activity that accompanies the sunspots can change the ultraviolet and soft X-ray emission levels, affecting Earth’s upper atmosphere. Some researchers have proposed that sunspots and solar activity are the main cause of global warming rather than carbon dioxide greenhouse gas emissions.

Bibliography

Izenman, Alan. “J R Wolf and the Zurich Sunspot Relative Numbers.” The Mathematical Intelligencer 7 (1985). http://astro.ocis.temple.edu/~alan/WolfMathIntel.pdf.

National Aeronautics and Space Administration. “The Sunspot Cycle.” http://solarscience.msfc.nasa.gov/SunspotCycle.shtml.

Spaceweather.com. “The Sunspot Number.” http://spaceweather.com/glossary/sunspotnumber.html.