On the Absence of Photospheric Net Currents in Vector Magnetograms of Sunspots Obtained From Hinode (SOT/SP)

TL;DR

This study analyzes high-resolution Hinode observations of 12 sunspots to investigate the presence of net electric currents, confirming their absence and supporting a fibril-bundle magnetic structure.

Contribution

It provides observational evidence from Hinode data that sunspots lack net electric currents, refining understanding of their magnetic field structure.

Findings

Azimuthal magnetic field varies in sign with azimuth.

Radial magnetic field varies in magnitude with azimuth.

Azimuthally averaged azimuthal component declines faster than 1/� in the penumbra.

Abstract

Various theoretical and observational results have been reported regarding the presence/absence of net electric currents in the sunspots. The limited spatial resolution of the earlier observations perhaps obscured the conclusions. We have analyzed 12 sunspots observed from Hinode (SOT/SP) to clarify the issue. The azimuthal and radial components of magnetic fields and currents have been derived. The azimuthal component of the magnetic field of sunspots is found to vary in sign with azimuth. The radial component of the field also varies in magnitude with azimuth. While the latter pattern is a confirmation of the interlocking combed structure of penumbral filaments, the former pattern shows that the penumbra is made up of a "curly interlocking combed" magnetic field. The azimuthally averaged azimuthal component is seen to decline much faster than 1/$\varpi$ in the penumbra, after an initial increase in the umbra, for all the spots studied. This confirms the confinement of magnetic fields and absence of a net current for sunspots as postulated by \cite{parker96}. The existence of a global twist for a sunspot even in the absence of a net current is consistent with a fibril-bundle structure of the sunspot magnetic fields.