Скачать или смотреть Simulations of Quiet Sun Magnetism

NCAR solar physicist Matthias Rempel with NCAR's High Altitude Observatory Division gave this talk on Sept. 3rd, 2014 as part of the HAO Colloquium Series.

Abstract:
Small-scale magnetic field is ubiquitous in the solar photosphere and in its properties mostly independent from the solar cycle, i.e., the large-scale field component. While likely both the large- and small-scale dynamos contribute to the observed magnetic field, recent research points toward a dominant contribution from a small-scale dynamo. In this talk I present a series of high-resolution small-scale dynamo simulations for the solar photosphere computed with the MURaM code. It is found that an efficient small-scale dynamo operating just in the uppermost layers of the convection zone is not sufficient. The observationally inferred level of quiet Sun magnetic field implies small-scale dynamo action throughout the solar convection zone across all scales. Under these circumstances there is no clear separation between small- and large-scale dynamo action, and vertical transport of mixed polarity magnetic field into the photosphere through convective upflows significantly influences the saturation field strength found in the photosphere. In contrast to that, a net magnetic flux imbalance (i.e., magnetic flux from active regions) is found to have only a weak influence on the amount of mixed-polarity field in the photosphere. While the observed quiet Sun magnetic field is generally regarded as rather weak, models that are consistent with observations imply a convection zone that is magnetized close to equipartition field strength. I will conclude my talk with a discussion of potential dynamical consequences from a magnetic field that reaches equipartition strength throughout most of the convection zone.