Research Highlight

What precedes sunspot cycles?

doi:10.1038/nindia.2009.70 Published online 27 February 2009

Researchers have developed a new solar model to explain why certain kinds of oscillations precede the orgy of periodic sunspot cycles1.

'Torsional oscillations' form deep inside the convection zone of Sun initiated by force on a point charge due to electromagnetic field (Lorentz force) spawned by varying magnetic fields of Sun. As these oscillations take place before sunspot cyles, insights into it can give clues to predict the intensity and periodicity of sunspot cycles, which can affect earth's atmosphere.

Torsional oscillations of a cycle begin a couple of years before the sunspots of that cycle at latitudes higher than where the first sunspots are subsequently seen. This fact intrigued researchers. To solve it, they developed a solar dynamo model and scribbled a code called SURYA. Dynamo model also known as flux transport dynamo allows for a much stronger magnetic field in the Sun's interior and the magnetic field generates flux tubes.

The torsional oscillation gets initiated in the lower footpoints of the vertical flux tubes, where the Lorentz force builds up due to the production of a specific magnetic field known as azimuthal magnetic field. This perturbation then propagates upward along the vertical flux tubes. The torsional oscillations seem to be present throughout the convection zone, which lies 150,000 km below the sun's surface.

Knowing the nature of torsional oscillations which begin 2-3 years before sunspot cycles is significant as during such cycles chunks of solar hot plasmas can make their way to earth disrupting radio communication and tripping power supply grids.

The authors of this work are from: Department of Theoretical Sciences, S. N. Bose Centre for Basic Sciences, Kolkata and Department of Physics, Indian Institute of Science, Bangalore, India.


  1. Chakraborty, S. et al. Why Does the Sun’s Torsional Oscillation Begin before the Sunspot Cycle? Phys. Rev. Lett. 102, 041102 (2009) | Article |