Inclinations of small quiet-Sun magnetic features based on a new geometric approach

Abstract

High levels of horizontal magnetic flux have been reported in the quiet-Sun internetwork, often based on Stokes profile inversions. Here we introduce a new method for deducing the inclination of magnetic elements and use it to test magnetic field inclinations from inversions. We determine accurate positions of a set of small, bright magnetic elements in high spatial resolution images sampling different photospheric heights obtained by the Sunrise balloon-borne solar observatory. Together with estimates of the formation heights of the employed spectral bands, these provide us with the inclinations of the magnetic features. We also compute the magnetic inclination angle of the same magnetic features from the inversion of simultaneously recorded Stokes parameters. Our new, geometric method returns nearly vertical fields (average inclination of around 14 deg with a relatively narrow distribution having a standard deviation of 6 deg). In strong contrast to this, the traditionally used inversions give almost horizontal fields (average inclination of 75+-8 deg) for the same small magnetic features, whose linearly polarised Stokes profiles are adversely affected by noise. The almost vertical field of bright magnetic features from our geometric method is clearly incompatible with the nearly horizontal magnetic fields obtained from the inversions. This indicates that the amount of magnetic flux in horizontal fields deduced from inversions is overestimated in the presence of weak Stokes signals, in particular if Stokes Q and U are close to or under the noise level. By combining the proposed method with inversions we are not just improving the inclination, but also the field strength. This technique allows us to analyse features that are not reliably treated by inversions, thus greatly extending our capability to study the complete magnetic field of the quiet Sun.

12 pages, 9 figures, 1 table; Accepted for publication in Astronomy & Astrophysics

References in corpus (12)

• A Substantial Amount of Hidden Magnetic Energy in the Quiet Sun
• A solar surface dynamo
• Quiet Sun internetwork magnetic fields from the inversion of Hinode measurements
• Small-scale solar magnetic fields
• Emergence of small-scale magnetic loops through the quiet solar atmosphere
• Strong horizontal photospheric magnetic field in a surface dynamo simulation
• Transient horizontal magnetic fields in solar plage regions
• Comparison of transient horizontal magnetic fields in a plage region and in the quiet Sun
• Low-lying magnetic loops in the solar internetwork
• Evidence for Quasi-isotropic Magnetic Fields from Hinode Quiet Sun Observations
• Structure and Dynamics of Isolated Internetwork Ca II H Bright Points Observed by Sunrise
• Pervasive Linear Polarization Signals in the Quiet Sun

Cited by in corpus (12)

• The Magnetic Field in the Solar Atmosphere
• Waves in the lower solar atmosphere: the dawn of next-generation solar telescopes
• Transverse Oscillations in Slender Ca II H Fibrils Observed with Sunrise/SuFI
• High-frequency Oscillations in Small Magnetic Elements Observed with Sunrise/SuFI
• Non-linear propagation of kink waves to the solar chromosphere
• Estimation of the magnetic flux emergence rate in the quiet Sun from Sunrise data
• Statistical evolution of quiet-Sun small scale magnetic features using Sunrise observations
• Three-dimensional magnetic structure of a sunspot: comparison of the photosphere and upper chromosphere
• The magnetic properties of photospheric magnetic bright points with high resolution spectropolarimetry
• Kinematics of Magnetic Bright Features in the Solar Photosphere
• The importance of horizontal Poynting flux in the solar photosphere
• Intensity contrast of solar network and faculae close to the solar limb, observed from two vantage points