Frequent Occurrence of High-speed Local Mass Downflows on the Solar Surface

TL;DR

This study reports frequent high-speed, possibly supersonic, magnetic field-associated downflows on the solar surface, observed with Hinode, revealing their connection to magnetic features and dynamic evolution in the photosphere.

Contribution

It provides new spectro-polarimetric evidence of transient high-speed downflows linked to various magnetic configurations on the solar surface, highlighting their role in magnetic field dynamics.

Findings

High-speed downflows occur near sunspot penumbral boundaries.

New types of downflows are found at sunspot umbra edges without penumbral structures.

Downflows are related to magnetic flux interactions and are transient.

Abstract

We report on new spectro-polarimetric measurements with simultaneous filter imaging observation, revealing the frequent appearance of polarization signals indicating high-speed, probably supersonic, downflows that are associated with at least three different configurations of magnetic fields in the solar photosphere. The observations were carried out with the Solar Optical Telescope onboard the {\em Hinode} satellite. High speed downflows are excited when a moving magnetic feature is newly formed near the penumbral boundary of sunspots. Also, a new type of downflows is identified at the edge of sunspot umbra that lack accompanying penumbral structures. These may be triggered by the interaction of magnetic fields sweeped by convection with well-concentrated magnetic flux. Another class of high speed downflows are observed in quiet sun and sunspot moat regions. These are closely related to the formation of small concentrated magnetic flux patches. High speed downflows of all types are transient time-dependent mass motions. These findings suggest that the excitation of supersonic mass flows are one of the key observational features of the dynamical evolution occurring in magnetic-field fine structures on the solar surface.