The dynamics of small-scale magnetic fields modulated by the solar cycle

In addition to sunspots, the most easily visualized manifestation of solar magnetism, cutting-edge observations of the solar atmosphere have uncovered a plethora of magnetic flux tubes, down to the resolving power of modern high-resolution telescopes (a few tens of kilometers), revealing how the Sun is a fully magnetized star. These magnetic elements are advected and buffeted by ambient plasma flows and turbulent convection, resulting in perturbations of the flux tubes that make them natural conduits for channeling wave energy into the upper layers of the Sun’s atmosphere and significantly contributing to the acceleration of the solar wind. Data acquired by the Helioseismic and Magnetic Imager (HMI) on board NASA’s Solar Dynamics Observatory (SDO) have made it possible to study the dynamics of small-scale magnetic fields over long timescales. Here, for the first time, we present the discovery of a modulation in the dynamical behavior of small-scale magnetic concentrations in the photosphere over temporal scales consistent with the solar activity cycle (i.e., 11 years), which has only been made possible by the long observing lifetime of the SDO/HMI spacecraft. Furthermore, we also find a temporal varying polarization of their perturbations on similar timescales. This demonstrates how the small-scale dynamics of magnetic fields are also affected by the global dynamo. These discoveries were realized through automated tracking of magnetic fields in the solar photosphere over 11 continuous years, resulting in the most extended statistical analysis of its kind so far, with more than 31 million magnetic concentrations examined.