The brightness of magnetic field concentrations in the quiet Sun

Abstract

In addition to the `facular' brightening of active regions, the quiet Sun also contains a small scale magnetic field with associated brightenings in continuum radiation. We measure this contribution of quiet regions to the Sun's brightness from high spatial resolution (0"16-0"32) observations of the Swedish 1-m Solar Telescope (SST) and Hinode satellite. The line-of-sight magnetic field and continuum intensity near \ion{Fe}{i} 6302.5 Å are used to quantify the correlation between field strength and brightness. The data show that magnetic flux density contains a significant amount of intrinsically weak fields that contribute little to brightness. We show that with data of high spatial resolution a calibration of magnetic flux density as a proxy for brightness excess is possible. In the SST data, the magnetic brightening of a quiet region with an average (unsigned) flux density of 10 G is about 0.15%. In the Hinode data, and in SST data reduced to Hinode resolution, the measured brightening is some 40% lower. With appropriate correction for resolution, magnetic flux density can be used as a reliable proxy in regions of small scale mixed polarity. The measured brightness effect is larger than the variation of irradiance over a solar cycle. It is not clear, however, if this quiet Sun contribution actually varies significantly. \keywords{Sun: surface magnetism -- photosphere -- solar-terrestrial relations}

A&A (in press)

References in corpus (5)

• CRISP Spectropolarimetric Imaging of Penumbral Fine Structure
• A Substantial Amount of Hidden Magnetic Energy in the Quiet Sun
• Strong horizontal photospheric magnetic field in a surface dynamo simulation
• Point spread functions for the Solar Optical Telescope onboard Hinode
• The intensity contrast of solar photospheric faculae and network elements II. Evolution over the rising phase of solar cycle 23

Cited by in corpus (7)

• Solar cycle variation in solar irradiance
• Total Solar Irradiance during the Last Five Centuries
• Photometric Properties of Network and Faculae Derived from HMI Data Compensated for Scattered-Light
• Small-scale dynamos on the solar surface: dependence on magnetic Prandtl number
• The dark side of solar photospheric G-band bright points
• Intensity contrast of solar network and faculae -- II. Implications for solar irradiance modelling
• Analysis and modeling of solar irradiance variations