Quantifying Solar Magnetic Field Evolution and Its Relation to Eruptions

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

The PI proposes to explore the relationship between solar eruptive phenomena, e.g., coronal mass ejections (CMEs), and flows and evolution in active region photospheric magnetic fields. Predicting the onset of these eruptive events is one of the major remaining challenges in space weather research. Many observers have reported that rotational and shearing flows, which can contribute energy to the coronal magnetic field, are present in eruptive active regions. Further, recent numerical simulations suggest that converging flows and magnetic flux cancellation in active regions containing twisted or sheared magnetic fields can initiate eruptions. However, rotation, shearing motions, and flux cancellation, as with active region flows in general, have only been quantitatively investigated in a few case studies. The PI will measure flows, rotation, shear, convergence, and cancellation in at least 30 active regions, to systematically explore relationships between field evolution and eruptive behavior. Her sample, chosen over the course of the solar cycle, will consist of regions that exhibit different types of behavior, from flares and CMEs, to filament disappearances, to low activity. By applying local correlation tracking (LCT) to SOHO/MDI and GONG+ line-of-sight (LOS) photospheric magnetograms, she will derive active region flows, and measure rotation, shearing, and convergence. The proposer will also apply LCT to SOLIS chromospheric LOS magnetograms when they become available, which will provide new perspectives and further constraints on the processes driving solar eruptions. She will apply inductive local correlation tracking (ILCT), a recently developed technique using LCT and the magnetic induction equation, to determine three-component photospheric velocity fields from SOLIS vector magnetograms. Using Cartesian-to-polar transformations, she will measure the rotational velocities of active region magnetic features, and compare them with LCT results. In addition, the PI will quantify flux cancellation rates, and study their variation around the time of eruptive events. The PI proposes to maintain and enhance the existing GONG+ related website at UC Berkeley. This study will also complement CME modeling efforts by others in the space weather community. Further, this investigation may enhance our capability to predict CMEs, the most powerful drivers of space weather, which play a unique role in the coupled Sun-Earth system. In addition, techniques developed here will be useful in analysis of data from current and future solar magnetographs.