The sun's magnetism presents major challenges to understand both how the observed 11-year cycles of magnetic activity are achieved and where the strong flux loops that break through the surface as…

The Regents of the University of Colorado, doing business as the University of Colorado Office of Contracts and Grants Division, has been awarded a $600,000.00 grant by the National Aeronautics and Space Administration (NASA) to conduct research on the origins of sunspots and the Sun's magnetic activity cycles. The grant supports the University's efforts to leverage recent advances in 3D magnetohydrodynamic (MHD) simulations to better understand the Sun's complex magnetic dynamo processes and how they drive the emergence of sunspot pairs. This research aligns with NASA's Heliophysics science goals related to understanding the Sun's activity and its impacts on the space environment. The grant was awarded without a set-aside designation and has a period of performance through June 25, 2025. As a leading public research university, the University of Colorado has a long history of conducting fundamental scientific research and providing technical expertise to federal agencies across the space, defense, and environmental domains.

The sun's magnetism presents major challenges to understand both how the observed 11-year cycles of magnetic activity are achieved and where the strong flux loops that break through the surface as sunspot pairs are actually formed. Clearly a magnetic dynamo is operating within the deep convection zone, yet sorting out how this zone's intensely turbulent flows yield orderly magnetic behavior reveals many puzzles. The clearest indicators of the sun's magnetic cycle are the sunspots which follow fairly orderly and systematic emergence patterns as the cycles proceed. Yet there is considerable uncertainty and debate as to where the toroidal flux loops originate that rise through the surface to form individual sunspot pairs, and indeed how they are formed in the first place. We are now in a position to address the origins of sunspots, informed by three recent advances in solar dynamo theory. Firstly, global 3-d MHD simulations carried out in full spherical shells, such as with our anelastic spherical harmonic (ASH) code, are showing that dynamo action can build wreaths of strong toroidal magnetic field in the bulk of the convection zone. This is contrary to beliefs that such ordered structures could not survive in the midst of the intense turbulence there. Secondly, our 3-d global simulations with full dynamical feedbacks are achieving dynamo cycles with regular reversals in the large-scale magnetic fields involving wreaths. Some exhibit equatorward propagation of toroidal flux during the cycles, reminiscent of the sun. Thirdly, we have found that loops of magnetic field can separate spontaneously from the wreaths through buoyancy instability and rise toward the surface, providing flux emergence from sites that had not previously been anticipated. We shall compare our statistics on rising loops with sunspot emergence properties obtained from recent detailed studies available of the continuous magnetogram images from 1995 onward by MDI on soho and now HMI on SDO. Our proposed work on the origin of sunspots ties into the first heliophysics decadal survey science goal ``determine the origins of the sun's activity and predict the variations in the space environment".