Bright points in the quiet Sun as observed in the visible and near-UV by the balloon-borne observatory Sunrise

TL;DR

This study uses high-resolution balloon-borne observations to measure bright points in the quiet Sun across visible and near-UV wavelengths, revealing their brightness contrasts and magnetic properties, including the highest contrast observed at 214 nm.

Contribution

First measurements of bright point contrasts below 388 nm in the quiet Sun, showing increased contrast at shorter wavelengths and detailed magnetic and flow properties.

Findings

Bright points reach up to five times the quiet Sun brightness at 214 nm.

All bright points are associated with magnetic signals, often weak.

Most bright points exhibit weak downflows, with some showing strong flows.

Abstract

Bright points (BPs) are manifestations of small magnetic elements in the solar photosphere. Their brightness contrast not only gives insight into the thermal state of the photosphere (and chromosphere) in magnetic elements, but also plays an important role in modulating the solar total and spectral irradiance. Here we report on simultaneous high-resolution imaging and spectropolarimetric observations of BPs using Sunrise balloon-borne observatory data of the quiet Sun at disk center. BP contrasts have been measured between 214 nm and 525 nm, including the first measurements at wavelengths below 388 nm. The histograms of the BP peak brightness show a clear trend toward broader contrast distributions and higher mean contrasts at shorter wavelengths. At 214 nm we observe a peak brightness of up to five times the mean quiet-Sun value, the highest BP contrast so far observed. All BPs are associated with a magnetic signal, although in a number of cases it is surprisingly weak. Most of the BPs show only weak downflows, the mean value being 240 m/s, but some display strong down- or upflows reaching a few km/s.