Influence of Low-Degree High-Order p-Mode Splittings on the Solar Rotation Profile

TL;DR

This study investigates how low-degree, high-order p-mode splittings, especially at higher frequencies, influence the accuracy of the solar rotation profile inferred from helioseismic data, emphasizing the importance of precise measurements.

Contribution

The paper provides a theoretical analysis of the impact of high-frequency, low-degree p-mode splittings on the solar rotation profile, highlighting the significance of measurement errors.

Findings

High-frequency, low-degree p modes carry crucial information about the solar core.

Measurement errors at high frequencies weaken constraints on the rotation profile.

Including high-frequency modes improves the understanding of the Sun's inner rotation.

Abstract

The solar rotation profile is well constrained down to about 0.25 R thanks to the study of acoustic modes. Since the radius of the inner turning point of a resonant acoustic mode is inversely proportional to the ratio of its frequency to its degree, only the low-degree p modes reach the core. The higher the order of these modes, the deeper they penetrate into the Sun and thus they carry more diagnostic information on the inner regions. Unfortunately, the estimates of frequency splittings at high frequency from Sun-as-a-star measurements have higher observational errors due to mode blending, resulting in weaker constraints on the rotation profile in the inner core. Therefore inversions for the solar internal rotation use only modes below 2.4 mHz for l < 4. In the work presented here, we used an 11.5 year-long time series to compute the rotational frequency splittings for modes l < 4 using velocities measured with the GOLF instrument. We carried out a theoretical study of the influence of the low-degree modes in the region 2 to 3.5 mHz on the inferred rotation profile as a function of their error bars.