Q-Maps: A New Synoptic Data Product for Investigating Dynamic Coronal Connectivity

The "squashing degree" Q parameter characterizes the local divergence of nearby magnetic field lines. It highlights separatrix and quasi-separatrix surfaces associated with the structural features of the magnetic field, such as null, bald-patch, and minimum points. These surfaces bound distinct flux systems and accommodate their evolution through magnetic reconnection. Its utility for understanding the magnetic configuration of the corona as it relates to space-weather activity has been demonstrated by many recent works. Here we describe a new data product: synoptic Q-maps using Helioseismic and Magnetic Imager (HMI) data since May 2010 as input. For global-scale field, we regularly compute 2D Q-maps at various heights based on a high-resolution potential field source surface (PFSS) model. At the upper boundary, these maps intuitively demonstrate the expansion of coronal holes, outlining their boundaries formed by streamers and pseudo-streamers. At lower heights, they additionally reveal an intricate network of closed (quasi-)separatrix surfaces that can also be involved in the multi-scale coronal dynamics driven by solar flares, coronal mass ejections, and solar wind. Future work includes calculations with global MHD models, using local active region models, and data visualization. The Q-maps will be available on the SDO/JSOC website and via the Virtual Solar Observatory.