What is the solar cycle?

Like a bar magnet, the Sun also has a magnetic field with north and south poles. The magnetic field exists due to the constant movement of electrically charged particles within the Sun. Every 11 years or so, the Sun’s magnetic field completely flips, meaning its north and south poles switch places. This periodic change is known as the solar cycle.

The solar cycle affects activity on the surface of the Sun. For instance, the Sun is at its most active when the magnetic field flips. This phase is called the solar maximum. During this period, the star can send out more frequent and intense bursts of radiation and particles into space. After the flip, the star calms down until it reaches the solar minimum, and a new cycle begins.

During the solar maximum, the Sun’s surface has the most number of sunspots —  small, dark and cooler areas where the magnetic field is particularly strong. During the solar minimum, the Sun has the least sunspots. Scientists track the solar cycle by counting the number of sunspots.

Moreover, “giant eruptions on the Sun, such as solar flares and coronal mass ejections, also increase during the solar cycle. These eruptions send powerful bursts of energy and material into space,” according to a report on NASA’s website. The bursts are significant as they can have an impact on Earth — they can disrupt satellite communication, and even affect electricity grids on the planet. That’s the reason why scientists keep a tab on the solar cycle.

Why are so many solar missions getting launched now?

The present solar activity and number of sunspots suggest that this cycle may be nearing its maxima, though the official confirmation of the same is yet to be made. According to the National Oceanic and Atmospheric Administration (NOAA), which is one of the organisations that track solar cycles, solar activities in this cycle picked up momentum around May 2022 and has continued to remain above normal through most of 2024.

The solar maximum is the best possible window available for physicists to both launch and observe the sun. This is precisely why there has been a spike in the missions to observe the star. Solar physicists are well aware if they miss this window, the next possible intense solar activity will not be before 2035-2036.

Which missions have been launched?

Since September 2023, two solar missions by India and the European Space Agency have been launched. These are

> Aditya L1, India: Launched on September 2, 2023

In September 2023, the Indian Space Research Organisation (ISRO) launched Aditya L1, the country’s first solar mission. It is designed to study solar flares and solar winds, measure low-intensity magnetic fields and solar soft X-ray flux, etc.

> Proba-3, European Space Agency: Launched on December 4, 2024

ISRO launched Proba-3, which has a unique design to study solar winds and solar storms.

> PUNCH, NASA: Launch on March 06, 2025

PUNCH is a first-of-its-kind solar mission that will study the solar corona — the outermost layer of the Sun’s atmosphere. Four identical suitcase-sized satellites will continuously image the Sun’s inner corona and provide origins of solar flares, etc.