In simple terms a solar cycle is the periodically repeating pattern in the solar activity. One solar cycle typically lasts for 11-years. In September 2020 NASA and the National Oceanic and Atmospheric Administration (NOAA) announced that Solar Cycle 25 has begun in December 2019. Solar activity is measured in terms of sunspots visible on the Sun’s surface. In the middle of the solar cycle, the number of these sunspots becomes greatest and this point in the solar cycle is called the Solar Maximum. After reaching the Solar Maximum, the solar activity begins to fade and number of sunspots gradually becomes smaller. The end of the solar cycle indicates the Solar Minimum when the least number of sunspots are visible. After Solar Minimum, a new solar cycle begins. Solar cycles may have significant effect on the life on Earth.
What is a Solar Cycle?
Sun‘s surface is a highly active place. Plasma and gases move around quickly in photosphere of the Sun. Electric properties of plasma generate magnetic field. Due to movement of plasma, these magnetic fields undergo all sorts transformations. This constant movement in plasma and Sun’s magnetic field is called the solar activity.
Definition: A solar cycle is the waxing and waning of the solar activity. One solar cycle lasts for about 11 years and it spans from one solar minimum to the next solar minimum.
Solar activity causes appearance of sunspots on the face of the Sun. More the solar activity, more will be the number of sunspots. Researchers estimate the extent of solar activity by counting the number of sunspots visible from Earth.
Apart from sunspots, solar activity causes other phenomena like coronal loops, prominences, and reconnection events on Sun’s surface.
Who Discovered the Existence of Solar Cycles?
Samuel Heinrich Schwabe, a German astronomer, studied the sunspots for 17 years and reached a conclusion in 1843 that solar activity exhibits a repetitive patterns. Therefore, Samuel Heinrich Schwabe is credited with discovering the solar cycles.
When was the First Solar Cycle?
Rudolf Wolf, a Swiss astronomer, compiled and studied the sunspot data up to the time of Galileo (who first observed the sunspots in 1609). Wolf reconstructed the solar activity based on this data. Based on the research done by Wolf, the period from 1755 to 1766 is termed as the first solar cycle.
Now the researchers have announced that the Solar Cycle 25 began in December 2019. The Solar Maximum of this cycle will arrive in July 2025.
How does the Solar Cycle Affects Life?
The solar activity in the beginning of a new solar cycle remains minimum. However as the solar cycle reaches the mid-point the solar activity becomes maximum. Increased solar activity can affect radio communication and satellite communication. Such communication problems can causes issues for marine and aircraft communication as well as for amateur radio operators and shortwave broadcasters.
Too much of solar radiations can also harm astronauts working outside of the International Space Station.
Some studies suggest that solar activity can affect global climate and human health. However, there are not conclusive evidence for this as yet.