Quiet-Sun intensity contrasts in the near ultraviolet

TL;DR

This study presents high-resolution near-ultraviolet images of the quiet Sun, revealing the highest intensity contrasts observed, and compares these with numerical simulations, highlighting areas of agreement and discrepancy.

Contribution

First high-resolution near-ultraviolet images of the quiet Sun from a balloon-borne telescope, providing new contrast measurements and comparison with simulations.

Findings

Quiet-Sun intensity contrasts reach up to 32.8% at 214 nm.

Good agreement between observations and simulations at 388 nm and 312 nm.

Discrepancies exist between observed and simulated contrasts at shorter wavelengths.

Abstract

We present high-resolution images of the Sun in the near ultraviolet spectral range between 214 nm and 397 nm as obtained from the first science flight of the 1-m Sunrise balloon-borne solar telescope. The quiet-Sun rms intensity contrasts found in this wavelength range are among the highest values ever obtained for quiet-Sun solar surface structures - up to 32.8% at a wavelength of 214 nm. We compare with theoretical intensity contrasts obtained from numerical magneto-hydrodynamic simulations. For 388 nm and 312 nm the observations agree well with the numerical simulations whereas at shorter wavelengths discrepancies between observed and simulated contrasts remain.