Helioseismic constraints on rotation and magnetic fields in the solar core

In recent years, more and more precise measurements have been made of solar oscillation frequencies and line widths. From space, the Solar and Heliospheric Observatory/Michelson Doppler Imager (MDI) data has led to much progress. From the ground, networks, like Global Oscillation Network Group (GONG), Taiwanese Oscillation Network (TON), and Birmingham Solar Oscillations Network (BiSON) have also led to much progress. The sharpened and enriched oscillation spectrum of data have been critically complemented by advances in the treatments of the opacities and the equation of state. All of this has led to a significantly more precise probing of the solar core. Here we discuss the progress made and suggest how the core may be better probed with seismic data on-hand. In particular, we review our knowledge of the rotation and structure of the core. We further argue that much may be learned about the core by exploiting the line width data from the aforementioned sources. Line-width data can be used to place sharper constraints on core properties, like the degree to which the Sun rotates on a single axis and the upper limit on magnetic fields that may be buried in the core.