Science Seminars

5/11/2017 – Lisa Upton; Modeling Active Region Evolution – at the Sun’s Surface and into the Corona

Speaker: Lisa Upton (UCAR)
Date: Monday, May 11, 2020
Time: 4:00 PM
Location: SPSC W120

Seminar Abstract:

The Advective Flux Transport (AFT) model is a state of the art Surface Flux Transport model, which simulates the observed near-surface flows (including an evolving convective flow velocity field) to model the transport of magnetic flux over the entire Sun. The STEREO mission provides the first opportunity to track the long-term evolution of Active Regions over multiple rotations. We illustrate how He 304 Å images can be used to validate the far-side evolution of individual active regions produced with AFT. We show that when new flux emergence occurs on the far-side of the Sun, 304 Å images can provide sufficient information about the active region to predict its evolution. We then present recent results in which we extend the radiance – magnetic flux power-law relationship to the AIA 335 °A passband, and the Fe XVIII 93.93 °A spectral line in the 94 °A passband. We use these results to test our current understanding of magnetic flux evolution and coronal heating by modeling the hydrodynamics of individual field lines with the Enthalpy-based Thermal Evolution of Loops (EBTEL) model including steady heating scaled as the ratio of the average field strength and the length (B/L). We find that steady heating is able to partially reproduce the EUV radiance – magnetic flux relationships and discuss how impulsive heating might be able to explain the discrepancies. This study demonstrates that combined models of magnetic flux transport, magnetic topology and heating can yield realistic estimates for the decay of active region radiances with time.