HMI Ring Diagram Analysis: Effects of tracking, noise and resolution

TL;DR

This paper investigates how tracking rates, noise, and resolution influence ring-diagram helioseismic analysis results, highlighting resolution as the most significant factor affecting data accuracy.

Contribution

It provides a systematic assessment of the impacts of tracking, noise, and resolution on ring-diagram analysis, with insights into optimal data processing parameters.

Findings

Resolution significantly affects ring-diagram results.

Doppler noise has minimal impact except at deep regions.

Tracking rate variations produce comparable effects to noise.

Abstract

Ring diagram analysis is a standard local helioseismic technique. Data from the Helioseismic and Magnetic Imager (HMI) on the Solar Dynamics Observatory (SDO) are routinely used for Ring-diagram analysis, and fits to the power spectra as well as inversion results are standard data products. In this paper we examine the effects of different tracking rates, noise, and resolution on ring-diagram results. Most of the analysis is for $15^\circ$ tiles, but we also examine the effects of different tile sizes. The largest effect we find is that of resolution. Doppler noise has very little effect on the results, except perhaps at the deepest regions for which the tiles can give reliable results; variations in the tracking rate have a similar effect.