Surface waves in solar granulation observed with {\sc Sunrise}

TL;DR

This study uses high-resolution observations from the Sunrise observatory to analyze solar oscillations, revealing how granulation and exploding granules contribute to the excitation of p-modes and the properties of small-scale waves.

Contribution

It provides new insights into the excitation mechanisms of solar p-modes, highlighting the role of exploding granules alongside intergranular lanes, using high-resolution Doppler velocity data.

Findings

Both standing and running waves are observed in Doppler data.

Exploding granules contribute to p-mode excitation.

High-degree small-scale waves are analyzed with Fourier filtering.

Abstract

Solar oscillations are expected to be excited by turbulent flows in the intergranular lanes near the solar surface. Time series recorded by the IMaX instrument aboard the {\sc Sunrise} observatory reveal solar oscillations at high resolution, which allow studying the properties of oscillations with short wavelengths. We analyze two times series with synchronous recordings of Doppler velocity and continuum intensity images with durations of 32\thinspace min and 23\thinspace min, resp., recorded close to the disk center of the Sun to study the propagation and excitation of solar acoustic oscillations. In the Doppler velocity data, both the standing acoustic waves and the short-lived, high-degree running waves are visible. The standing waves are visible as temporary enhancements of the amplitudes of the large-scale velocity field due to the stochastic superposition of the acoustic waves. We focus on the high-degree small-scale waves by suitable filtering in the Fourier domain. Investigating the propagation and excitation of $f$- and $p_1$-modes with wave numbers $k > 1.4$\thinspace 1/Mm we find that also exploding granules contribute to the excitation of solar $p$-modes in addition to the contribution of intergranular lanes.