MAGNETIC HELICITY INJECTION BY HORIZONTAL FLOWS IN THE QUIET SUN. I. MUTUAL-HELICITY FLUX

摘要

The flux of magnetic helicity through the solar photosphere has implications in diverse areas of current solar research, including solar dynamo modeling and coronal heating. In this work, we focus on the flux of magnetic helicity from quiet-Sun magnetic fields. We express the total helicity flux in terms of mutual and self-helicities, which arise from relative motions of separate flux elements and from internal motions within individual magnetic flux elements, respectively. Using a novel labeling algorithm and a tracking algorithm applied to high-cadence, high-resolution Solar and Heliospheric Observatory Michelson Doppler Imager magnetograms, we determine the observed mutual-helicity flux density in the quiet Sun to be ～5 x 10~(12) Mx~2 cm~(-2) s~(-1) and compare this value with a simple theoretical prediction. The observed rate corresponds to a whole-cycle, hemispheric mutual-helicity flux of ～10~(43) Mx~2 from the quiet Sun, meaning that helicity injection by surface motions in quiet-Sun fields is negligible compared to the active region helicity flux rate.