Apr 11, 2012

Maria Weber, Colorado State University & High Altitude Observatory

"Comparing Simulations of Rising Flux Tubes through the Solar Convection Zone with Observations of Solar Active Regions "

It is a widely held belief that the large scale toroidal magnetic field responsible for the formation of solar active regions is amplified and stored near the base of the solar convection zone. This magnetic field must traverse the convection zone in order to emerge at the solar surface to form the active regions observed on the Sun. Thus answering the question of how active region scale flux tubes rise through the convection zone to eventual emergence at the solar surface is vitally important in the development of solar dynamo theory. To address this question, we utilize a thin flux tube model, initiated with a variety of magnetic field strengths, magnetic flux, and latitudes, embedded in a rotating spherical shell of turbulent solar-like convection. We compare the results of our simulations to observed properties of solar active regions, such as: tilt angles with respect to the east-west direction, the magnetic field asymmetry between the leading and following portions of an active region, and the rotation rate of active regions with respect to the surrounding plasma. In addition, we note that with convective influences, the rise times of the flux tubes are drastically reduced (from years to months), loops are able to emerge at low latitudes near the equator, and often emerge to produce active longitudes and clusters. We discuss how these diagnostic properties constrain the magnetic field strength at which the solar dynamo operates, and highlight the particular influences convection has on the dynamic evolution of active region scale flux tubes.