Coronal Magnetic Field Evolution from 1996 to 2012: Continuous Non-Potential Simulations

TL;DR

This study extends coupled flux transport and magneto-frictional simulations to model the continuous evolution of the solar corona's magnetic field over 15 years, providing insights into magnetic structure and energy buildup beyond traditional extrapolation methods.

Contribution

It introduces a more efficient numerical grid and calibration method for long-term simulations of the solar corona's magnetic field, capturing electric currents and free magnetic energy build-up.

Findings

Standard flux transport models are insufficient for Cycle 23 polar fields.

Flux ropes are more common outside active latitudes.

Active latitude flux ropes are more frequently ejected.

Abstract

Coupled flux transport and magneto-frictional simulations are extended to simulate the continuous magnetic field evolution in the global solar corona for over 15 years, from the start of Solar Cycle 23 in 1996. By simplifying the dynamics, our model follows the build-up and transport of electric currents and free magnetic energy in the corona, offering an insight into the magnetic structure and topology that extrapolation-based models can not. To enable these extended simulations, we have implemented a more efficient numerical grid, and have carefully calibrated the surface flux transport model to reproduce the observed large-scale photospheric radial magnetic field, using emerging active regions determined from observed line-of-sight magnetograms. This calibration is described in some detail. In agreement with previous authors, we find that the standard flux transport model is insufficient to simultaneously reproduce the observed polar fields and butterfly diagram during Cycle 23, and that additional effects must be added. For the best-fit model, we use automated techniques to detect the latitude-time profile of flux ropes and their ejections over the full solar cycle. Overall, flux ropes are more prevalent outside of active latitudes but those at active latitudes are more frequently ejected. Future possibilities for space-weather prediction with this approach are briefly assessed.