Radio Signature of Higher Atmospheric Meridional Flow and Implications for Magnetic Trees in the Sun

TL;DR

This study detects poleward plasma flows at chromospheric heights using 27 years of radio imaging, linking surface magnetic flux transport to deep-seated solar magnetic dynamics and supporting the magnetic tree hypothesis.

Contribution

First observational evidence of chromospheric poleward flows at 3000 km height reflecting subsurface meridional circulation, supporting magnetic connectivity models.

Findings

Detected poleward flow of 5-15 m/s at 3000 km altitude.

Flow patterns mirror photospheric meridional circulation.

Brightness feature motion correlates with magnetic flux transport.

Abstract

The coupling between plasma flows and magnetic fields in the solar atmosphere governs the transport of angular momentum and the redistribution of magnetic flux, yet its manifestation in the magnetically dominated upper chromosphere remains uncertain. Using 27 years of 17 GHz full-disk solar radio imaging observations from the Nobeyama Radioheliograph, we report the first detection of a poleward flow signature at heights of $3000\pm500$ km, an altitude where plasma magnetohydrodynamics expects magnetic dominance ($\beta<1$). The derived latitudinal velocity profile ($5-15$ m/s) mirrors the established photospheric meridional circulation, displaying modulation with solar cycle parameters. Comparison with long-term synoptic magnetograms reveals that the motion of 17 GHz brightness features closely tracks poleward magnetic flux transport, implying a deep magnetic anchoring of these structures. This finding provides the first observational evidence that chromospheric flows at radio wavelengths reflect subsurface meridional dynamics, consistent with the "magnetic tree" hypothesis, which links high-altitude motion to deep-seated magnetic connectivity.