Thursday 10 Jul 2014: 3D Dynamo Models of the Solar Cycle (THU)
Dr Mark Miesch - High Altitude Observatory, National Center for Atmospheric Research
Physics, 4th floor 14:00-15:00
For well over a century, understanding the origins of the 11-year solar activity cycle has remained at the forefront of solar physics. The hydromagnetic dynamo that lies at its heart produces the magnetic fields that regulate the variable electromagnetic and particle radiation of the Sun, including eruptive events such as solar flares and coronal mass ejections. This variability in turn regulates solar-terrestrial interactions, with practical consequences for our technological society. At the same time, the Sun is a classical example of an astrophysical dynamo with unparalleled observational scrutiny; we see here more than anywhere else how turbulent plasma motions can generate chaotic yet ordered magnetic fields on a colossal scale.
Modeling this complex system is a formidable challenge but two distinct dynamo paradigms have emerged as leading contenders to account for the origins of the solar cycle. These include Babcock-Leighton dynamo models and convective dynamo models. Both paradigms have their origins in theoretical work dating back more than half a century but continue to provide new insights as ongoing advances in high-performance computing technology fuel increasingly sophisticated and realistic model developments. In this talk I will review recent modeling work spanning both paradigms. After a brief review of magnetic cycles in convective dynamos, I will devote much of the talk to describing a novel 3D Babcock-Leighton dynamo model in which sunspots play an essential role. I will also describe complementary modeling efforts designed to elucidate the four fundamental dynamo ingredients, namely the differential rotation, the meridional circulation, the efficiency of convective transport and field generation, and the process of flux emergence. With this as a backdrop, I will more generally assess the current status of solar dynamo modeling and where it may be headed.