Quantifying Properties of Photospheric Magnetic Cancellations in the Quiet Sun Internetwork

TL;DR

This study investigates small-scale magnetic cancellations in the quiet Sun photosphere using spectropolarimetric data, quantifying flux, velocities, and lifetimes, and providing insights into magnetic flux evolution.

Contribution

It offers the first detailed characterization of magnetic cancellation events in the quiet Sun using high-resolution spectropolarimetric data and advanced feature tracking.

Findings

Average flux cancellation per event: 1.6×10^{16} Mx

Average cancellation rate: 3.8×10^{14} Mx s^{-1}

Average event lifetime: 9.2 minutes

Abstract

We analyzed spectropolarimetric data from the Swedish 1-meter Solar Telescope to investigate physical properties of small-scale magnetic cancellations in the quiet Sun photosphere. Specifically, we looked at the full Stokes polarization profiles along the Fe I 557.6 nm and of the Fe I 630.1 nm lines measured by CRisp Imaging SpectroPolarimeter (CRISP) to study temporal evolution of the line-of-sight (LOS) magnetic field during 42.5 minutes of quiet Sun evolution. From this magnetogram sequence, we visually identified 38 cancellation events. We then used Yet Another Feature Tracking Algorithm (YAFTA) to characterize physical properties of these magnetic cancellations. We found on average $1.6\times10^{16}$ Mx of magnetic flux cancelled in each event with an average cancellation rate of $3.8\times10^{14}$ Mx s$^{-1}$. The derived cancelled flux is associated with strong downflows, with an average speed of $V_\mathrm{LOS}\approx1.1$ km s$^{-1}$. Our results show that the average lifetime of each event is $9.2$ minutes with an average $44.8\%$ of initial magnetic flux being cancelled. Our estimates of magnetic fluxes provide a lower limit since studied magnetic cancellation events have magnetic field values that are very close to the instrument noise level. We observed no horizontal magnetic fields at the cancellation sites and therefore can not conclude whether the events are associated structures that could cause magnetic reconnection.