Time series of high resolution photospheric spectra in a quiet region of the Sun. II. Analysis of the variation of physical quantities of granular structures

TL;DR

This study analyzes high-resolution solar photospheric spectra to understand the physical and dynamic properties of granular structures, revealing how temperature and velocity vary with height and size of granules.

Contribution

It provides a detailed stratification model of granules and intergranular lanes, including temperature, velocity, pressure, and density, based on spectroscopic inversion data.

Findings

Temperature fluctuations decay with height.

Smaller granules penetrate less into higher layers.

Temperature contrast inverts beyond log tau = -1.

Abstract

From the inversion of a time series of high resolution slit spectrograms obtained from the quiet sun, the spatial and temporal distribution of the thermodynamical quantities and the vertical flow velocity is derived as a function of logarithmic optical depth and geometrical height. Spatial coherence and phase shift analyzes between temperature and vertical velocity depict the height variation of these physical quantities for structures of different size. An average granular cell model is presented, showing the granule-intergranular lane stratification of temperature, vertical velocity, gas pressure and density as a function of logarithmic optical depth and geometrical height. Studies of a specific small and a specific large granular cell complement these results. A strong decay of the temperature fluctuations with increasing height together with a less efficient penetration of smaller cells is revealed. The T -T coherence at all granular scales is broken already at log tau =-1 or z~170 km. At the layers beyond, an inversion of the temperature contrast is revealed. Vertical velocities are in phase throughout the photosphere and penetrate into the highest layers under study.