The strength of the magnetic field is one of the parameters that characterize a solar cycle. Other related phenomena also need to be considered. These include coronal mass ejections, eruptions, and solar winds, not to mention the famous black spots.
These related phenomena are often rare during periods of solar minimum. However, they are stronger and more common during periods of high solar activity. Fluctuations in the sun’s magnetic field can take place over dramatically different time scales – from seconds to billions of years. When researchers speak of a slowdown or rest period in solar activity, it does not mean that the star will stop shining.
A magnetic field reversal every 11 years
The sun has a certain rhythm of about 11 years in which its polar magnetic field reverses its polarity. The sharp decline in sunspots serves as an indicator for this change. Galileo was the first to observe sunspots in detail.
Many scientists then turned their attention to the latter, as well as the cyclical nature of their appearance and disappearance. In 1848 the Swiss astronomer Rudolf Wolf calculated the 11-year cycle based on the results of earlier research. He also invented a mathematical method to count the number of sunspots. Note that the Wolf number is always used to quantify solar activity.
In 2020, Cycle 25 had 80% more total sunspots than the corresponding period of Cycle 24, Photo Credit: Shutterstock / JoeZ
A more intense cycle than the previous one
The calculation of the solar cycles began with the birth of Wolf’s formula. Since then, each cycle has been numbered one by one. We are currently in the Sun’s 25th cycle of activity, which began in December 2019. On the other hand, the spots may not appear, a sign of slow motion solar activity.
This picture compares the sun at its most active level (solar maximum) and its least active level (solar minimum). Photo credit: NASA / SDO
Among other things, this was the case on 80 days of the first six months of the current cycle. Cycle 24 experienced the same phenomenon, but on a larger scale, namely 281 days with no spots. In 2020, cycle 25 had 80% more sunspots than the corresponding period in cycle 24. The current cycle therefore appears to be stronger. Meanwhile, the International Solar Cycle 25 Forecasting Panel expects to be about as strong as the previous cycle.
Are Magnetic Storms Coming?
Successful prediction of solar activity remains essential to assess the level of reliability of scientific theories about how our star works. There is also a more urgent and essential reason for this. Solar flares and coronal mass ejections can, depending on their intensity, disrupt our technological world.
After an 11 year cycle with no major eruption, magnetic storms or geomagnetic storms can occur over the sun and reach the earth and bombard our planet with charged particles. Fortunately, our planet’s protective barrier is strong enough to protect us from such dangers. “These storms are great to watch, but they cannot harm our organism as long as we stay on the surface of the earth, where we are protected by the earth’s shield,” notes Earthsky.org.