Vector Magnetic Fields and Current Helicities in Coronal Holes and Quiet Regions

TL;DR

This study uses Hinode observations to compare vector magnetic fields, current densities, and helicities in coronal holes and quiet regions, revealing that coronal holes have stronger and more inclined magnetic fields, indicating nonpotential magnetic structures.

Contribution

First detailed comparison of vector magnetic fields and current helicities in coronal holes and quiet regions using Hinode data.

Findings

Coronal holes have larger horizontal magnetic fields and current helicities than quiet regions.

Areas with high current helicity are co-spatial with strong magnetic field elements.

Magnetic fields in both regions are nonpotential, especially in strong field concentrations.

Abstract

In the solar photosphere, many properties of coronal holes (CHs) are not known, especially vector magnetic fields. Using observations from \emph{Hinode}, we investigate vector magnetic fields, current densities and current helicities in two CHs and compare them with two normal quiet regions (QRs) for the first time. We find that, in the CHs and QRs, the areas where large current helicities are located are mainly co-spatial with strong vertical and horizontal field elements both in shape and location. In the CHs, horizontal magnetic fields, inclination angles, current densities and current helicities are larger than those in the QRs. The mean vertical current density and current helicity, averaged over all the observed areas including the CHs and QRs, are approximately 0.008 A m$^{-2}$ and 0.005 G$^{2}$ m$^{-1}$, respectively. The mean current density in magnetic flux concentrations where the vertical fields are stronger than 100 G is as large as 0.012 $\pm$ 0.001 A m$^{-2}$, consistent with that in the flare productive active regions. Our results imply that the magnetic fields, especially the strong fields, both in the CHs and QRs are nonpotential.