Researchers at India’s Center of Excellence for Space Sciences at IISER Kolkata have discovered a new connection between the Sun’s magnetic field and the sunspot cycle that could help predict when peak solar activity will occur. Their study shows that the maximum intensity of solar cycle 25, the current sunspot cycle, is imminent and will likely occur within a year. The new study appears here: Monthly Notices of the Royal Astronomical Society: Letters.

Our star, the Sun, consists of hot ionized gas known as plasma. Large plasma flows and convection together create magnetic fields inside the Sun that appear as dark spots on the surface. These sunspots are comparable in size to Earth and are sources of intense magnetism, approximately 10,000 times stronger than Earth’s magnetic field.

Sometimes the magnetic fields of sunspots are disrupted by powerful events such as explosions or coronal mass ejections, giving rise to solar magnetic storms. These storms emit high-energy radiation and launch large amounts of magnetized plasma into outer space. The strongest of these storms, if directed towards Earth, could cause serious damage to orbiting satellites, power grids, and telecommunications.

Centuries of observations since the early 1600s show that the number of sunspots observed on the Sun changes periodically. Approximately every 11 years, the number and intensity of spots of solar activity reach their peak, when the strongest perturbations in the planetary space environment or space weather are expected. But predicting when this peak will occur has remained a difficult task.

The solar cycle is created by a dynamo mechanism driven by the energy of plasma flows within the Sun. This dynamo mechanism is believed to involve two main components of the Sun’s magnetic field; one of them occurs in the sunspot cycle, the other in the recycle of the Sun’s large-scale dipole field; the latter is very similar to the Earth’s magnetic field; It extends from one pole of the Sun to the other. With the sunspot cycle, the Sun’s dipole field also grows and shrinks, and the north and south magnetic poles switch places every 11 years.

In 1935, Swiss astronomer Max Waldmaier discovered that the faster the sunspot cycle rate, the stronger their strength, so stronger cycles take less time to reach peak intensity. This relationship has often been used to estimate its strength based on observations of the early rising phase of the sunspot cycle.

This discovery complements the Waldmayer effect by connecting two major components of the Sun’s magnetic field and supporting the theory that sunspot evolution is an integral part of the functioning of the solar dynamo process, and not just a symptom of it.

These new observations of the rate of decline of the Sun’s dipole magnetic field can be combined with observations of sunspots to predict when the current cycle will peak. The analysis shows that the 25th maximum of the solar cycle will likely occur in early 2024, with uncertainty in the forecast shifting through September 2024. This latest discovery opens a new window for predicting the timing of peak solar cycles, when the most intense activity and most frequent space weather disturbances are expected.