Understanding the solar activity cycle remains one of the key problems in solar physics. Observed magnetic activities, such as sunspot cycles and magnetic field reversals, produce solar flares and coronal mass ejections, with significant influences on the Earth. Physicists generally believe that a magnetohydrodynamic dynamo produces the observed 11-year activity cycle by generating and changing magnetic fields in the solar convection zone (the outer 30% of the Sun).
Progress has been made in solar dynamo theory to the point that computational models may now be used as predictive tools (to a certain extent). The solar dynamo depends on the shearing, buoyancy, twisting and flows of magnetic plasma, the hot ionized gas that makes up the Sun. One of the least understood aspects of the solar dynamo concerns a material property of the Sun itself - the magnetic diffusivity, which contributes to changes in magnetic fields, and is itself changed by dynamic magnetic fields. A more complete understanding of the magnetic diffusivity in the convection zone, and of its effects on the evolution of solar magnetic fields, is required to more fully understand the solar dynamo. This is not only an interesting theoretical problem in solar physics and magnetohydrodynamics, it is also of practical importance to technologies that are sensitive to solar activity (from communications satellites to power grids), and to understanding the impact of the variable Sun on our biosphere.
Here, a proven solar dynamo model will be improved to better predict future solar cycles. The two dimensional, nonlinear, kinematic flux-transport dynamo model will be used to investigate the detailed causes and effects of diffusivity variations in radius, latitude, and time, due to factors such as temperature, turbulence, and changes in the local magnetic field strength. Dr. Zita will carry out investigations that will include important new physics such as dynamical magnetic quenching of diffusivity, and magnetic advection due to diffusivity gradients. Systematic evaluation of each effect, and comparison with other key dynamo elements, will deepen insight into the fundamental mechanisms of the solar dynamo.
Her investigations will contribute directly to key goals in solar physics, including understanding how magnetic fields appear, distribute, and disappear from their origin in the solar interior; and quantification of the physics, dynamics, and behavior of the system over the solar cycle. The research will produce (1) physics-based diffusivity models for use by solar dynamo modelers and (2) an improved dynamo model for prediction of future solar cycles.
This work can also illuminate dynamos in other stars, galaxies, and fusion plasmas; and mechanisms by which magnetic energy can be transformed into heat in the solar chromosphere and corona, as these all require better understanding of magnetic diffusivity. Undergraduates will be directly involved in the research at all stages. Ongoing scientific collaborations with the High Altitude Observatory at the National Center for Atmospheric Research will give students access to high quality research experiences. Dr. Zita is also active in public science literacy and science outreach to girls, and her home institution is a pioneer in outreach to students from underrepresented groups. Research projects such as the work supported here are routinely integrated into interdisciplinary college curricula. Finally, the project will strengthen the infrastructure for solar physics research, established in recent years at Evergreen College in the collaboration with the High Altitude Observatory.
