High speed magnetized flows in the quiet Sun

TL;DR

This study investigates magnetized flows in the quiet Sun using Hinode data, revealing their structure, evolution, and physical parameters, and suggests they are driven by siphon flows along magnetic loops.

Contribution

It provides detailed analysis of magnetized flow events, including their magnetic structure, atmospheric stratification, and evolution, using spectropolarimetric inversions and time series data.

Findings

Blue-shifted events occur over bright granule edges.

Red-shifted events are found over dark intergranular lanes.

Magnetic structures resemble Ω-loops with footpoints over granules and lanes.

Abstract

We have examined the spatial and polarimetric properties of these events using a variety of data from the Hinode spacecraft. We have also inferred the atmospheric stratification of the physical parameters by means of the inversion of the observed Stokes profiles employing the Stokes Inversion based on Response functions (SIR) code. Finally, we analyzed their evolution using a time series from the same instrument. Blue-shifted events tend to appear over bright regions at the edge of granules, while red-shifted events are seen predominantly over dark regions on intergranular lanes. Large linear polarization signals can be seen in the region that connects them. The magnetic structure inferred from the time series revealed that the structure corresponds to a $\Omega$-loop, with one footpoint always over the edge of a granule and the other inside an intergranular lane. The physical parameters obtained from the inversions of the observed Stokes profiles in both events show an increase with respect to the Harvard-Smithonian reference atmosphere in the temperature at $\log\tau_{500} \in (-1, -3)$ and a strong magnetic field, $B \ge 1$ kG, at the bottom of the atmosphere that quickly decreases upward until vanishing at $\log\tau_{500} \approx -2$. In the blue-shifted events, the line of sight velocities change from upflows at the bottom to downflows at the top of the atmosphere. Red-shifted events display the opposite velocity stratification. The change of sign in line of sight velocity happens at the same optical depth in which the magnetic field becomes zero. The physical mechanism that best explains the inferred magnetic field configuration and flow motions is a siphon flow along an arched magnetic flux tube. Further investigation is required however, as the expected features of a siphon flow cannot be unequivocally identified.