Sunspots

Sunspots are dark structures on the sun's surface caused by strong magnetic fields. A sunspot consists of a core, the umbra, and the penumbra (see graphic below). The sun's magnetic field lines emerge or enter here. The spots vary in shape and size. The occurrence of sunspots depends on the sun's 11-year cycle (see below).

In complex sunspot groups, tensions develop that can lead to strong eruptions. Plasma is hurled into space and ultimately causes auroras on Earth. The magnetic configuration of a sunspot group is crucial.

The magnetic classification (Mount Wilson Sunspot Magnetic Classification) of a sunspot group provides insight into how complex the sunspot group is. The more complex a group is, the more likely it is to produce strong flares. The magnetic classification is as follows: 

• Alpha (α)
  a unipolar group
• Beta (β)
  bipolar group that has a simply separated positive & negative part
• Gamma (γ)
  bipolar group that is irregularly distributed so that it cannot be classified as an Alpha or Beta group
• Beta-Gamma (β-γ)
  bipolar group that is so complex that no line can be drawn between parts with different polarity
• Delta (δ)
  umbrae with opposite polarity within a penumbra
• Beta-Delta (β-δ)
  sunspot with a beta part that contains one (or more) delta parts
• Beta-Gamma-Delta (β-γ-δ)
  sunspot with a beta-gamma part that contains one (or more) delta parts
• Gamma-Delta (γ-δ)
  sunspot with a gamma part that contains one (or more) delta parts

The table above shows the past sunspot cycles with their beginning and maximum. As already mentioned above, the maximum can vary. It can be stronger or weaker. Additionally, a cycle can have two maxima. If a cycle has two maxima, it is called a double peak. Such a double peak could be observed, for example, in cycle 23. If we are at the maximum of a sunspot cycle, the probability that strong auroras can be observed in Germany increases.