What are sunspots and why do they peak periodically?

Fluctuations in the number of spots on the solar disk are the most noticeable manifestation of the solar activity cycle. The spots themselves have been noticed since antiquity, astronomers began to observe them regularly in the 16th century, but only in 1843 did Rudolf Wolf discover an 11-year cycle. He was able to restore this cyclic sequence until the middle of the 18th century, until 1749, when the cycle began, which was assigned the number 1.

The appearance of sunspots – areas with very strong magnetic fields that appear darker – is associated with the “horizontal” component of the solar magnetic field. In addition to the Earth-like dipole field, the Sun has a horizontal field component, which appears due to the different rotation speeds of the outer and inner layers.

When the outer leads the inner, they pull the magnetic field lines with them, forming a horizontal component. In zones where the tubes of this field come to the surface, sunspots appear.

A large number of sunspots is accompanied by other manifestations of solar activity: X-ray solar flares, coronal mass ejections, coronal holes. These phenomena lead to disturbances in the solar wind, which in turn affects the Earth’s magnetic field, generating geomagnetic storms and auroras.

In periods when there are few or no spots at all – during a minimum of solar activity – all these events come to naught. Then the spots appear again, activity begins to grow, but these are already spots of a new solar cycle – they have the opposite magnetic polarity and appear closer to the poles, and then, as the cycle “ages”, they fall lower and lower towards the equator.

Scientists recorded a powerful M1.1 solar flare

The Sun is currently in its 25th activity cycle, which began in 2020. An increase in the activity of the luminary is manifested in an increase in the number of spots and the occurrence of flares and coronal mass ejections.

Sunspot region 2936 produced an M1.1 solar flare which peaked at 23:32 UTC. LASCO shows a slow asymmetrical full halo coronal mass ejection leaving the Sun. The bulk is heading north-east but we do expect this cloud to impact Earth in a few days. More info later. pic.twitter.com/WqMIWHNUAY

— SpaceWeatherLive (@_SpaceWeather_) January 30, 2022

If the plasma ejected from the Sun reaches the Earth, then a geomagnetic storm may occur, due to which auroras are observed in the sky, interference in radio communications, and failures in the operation of satellites and power systems occur.

Now the largest sunspot group on the Sun is AR2936, which recently quadrupled in size in just 48 hours. In the early hours of January 30, 2022, AR2936 generated an M1.1-class flare and an associated slow, asymmetric coronal mass ejection.

M-class flares are considered medium in strength and are capable of causing short-term disruptions in radio communications that affect the polar regions of the Earth.

In this case, the flare lasted more than 4 hours, which allowed astronomers to attribute it to the class of events of the LDE (Long Duration Event) type, which differ from short-term (several tens of minutes) X-ray flares in that they demonstrate a large or complex structure of the radiation source in the soft X-ray range and a gradual drop in the intensity of hard X-rays.

Scientists expect the plasma ejection to reach Earth on February 2, triggering a moderately severe Level 2 (G2) geomagnetic storm. During such storms, auroras can be observed above the Arctic Circle, descending to lower latitudes.

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Sources:

• Byrd, D. (2022, January 31). Big sunspot region AR2936 has blasted a CME toward Earth. EarthSky.
• King, B. (2022, January 30). Astro Bob: Big sunspot spins into view. Duluth News Tribune.

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Source: Curiosmos