Sunspot numbers are at their highest level in 20 years
The number of sunspots changes over the course of a cycle. Often, there are no spots visible for months at a time. However, there are currently more visible than there have been in decades. The cause is strengthened magnetic fields that hinder a process.
The number of dark sunspots is currently as high as it has been in 20 years. "We are currently at the maximum of a relatively strong solar cycle," explains solar physicist Achim Gandorfer from the Max Planck Institute for Solar System Research in Göttingen. The number of spots is dependent on solar activity, which changes within an eleven-year cycle. "Whether we are already at the end of the cycle or if there will be another increase, cannot be said at the moment."
The spots are caused by temperature differences on the surface, as Gandorfer explains. "The sun is a layered gas ball. Energy is generated in the interior, and the hot gas rises." At the surface, the energy is radiated, and the temperature of the matter drops suddenly. "The gas then sinks back in a cooler and denser form." This cycle is also called convection. However, it can happen that locally strengthened magnetic fields prevent the cooler gas from sinking, says Gandorfer. As a result, the cooler matter remains on the surface for longer periods.
Therefore, the spots are about 4000 degrees cooler than the surrounding surface, which is about 6000 degrees. "The spots are still very, very hot, but they appear darker in contrast because the surroundings are even hotter and brighter." While there are often no spots for months at a time, there can be hundreds during peak periods, says the expert. He speaks of the so-called sunspot relative number. It is calculated from the sum of individual spots plus the number of spot groups, each weighted by a factor of ten.
"Due to the weighting, the number is higher, we actually see fewer spots," adds Gandorfer. Moreover, a part of the spots is always on the side of the sun facing away from the Earth. In this cycle, the so-called sunspot relative number reached a maximum of 160 to 170, while in the previous cycle, the number was 130. Anyone who wants to look at the sunspots should only do so with appropriate protective equipment such as certified glasses or telescopes with protective filters. Otherwise, severe eye damage can occur.
The increase in visible sunspots is attributed to strengthened magnetic fields, as solar physicist Achim Gandorfer explains. Within the eleven-year solar cycle, changes in the number of sunspots are largely dependent on solar activity.
