zonnevlekactiviteit

Zonnevlekactiviteit refers to the variation in the frequency and characteristics of sunspots observed on the solar photosphere. Sunspots are regions of intense magnetic field that appear darker than the surrounding photosphere because they are cooler. Their formation and evolution reflect the Sun’s magnetic dynamo processes, with the magnetic field reversing polarity approximately every 11 years. This period, called the solar cycle, is monitored through the international sunspot number, a long‑term index that counts both the number of individual spots and groups of spots.

During the ascending phase of a cycle the sunspot number rises, leading to increased solar magnetic activity, enhanced solar flares and coronal mass ejections. The peak of the cycle is known as solar maximum. In the descending phase the sunspot count falls, resulting in reduced solar emissions and a quieter heliosphere, what astronomers call the solar minimum. Solar cycle 24, which began in December 2008, reached a maximum in March 2014, and the next cycle started in December 2019.

Sunspot activity directly influences the Sun’s radiative output. The total solar irradiance (TSI) fluctuates by about 0.1% over a solar cycle. Variations in ultraviolet emission and solar wind parameters can alter the Earth’s upper atmosphere, affect satellite operations, and modulate cosmic ray flux reaching the troposphere, with a potential, although still debated, link to climate variability. Space‑weather forecasting agencies use sunspot numbers and magnetogram data to forecast geomagnetic storms that can interfere with power grids, radio communications, and navigation systems.

The study of zonnevlekactiviteit combines observations from ground‑based sunspot archives, spacecraft missions such as SOHO, SDO, and ground‑based magnetographs. Modern modeling of the solar dynamo seeks to predict future cycles, but the timing, amplitude, and profile of each cycle remain subjects of active research.