Spatial Cross Spectrum: Reducing Incoherent Convective Background of Resolved Heloseismic Instruments

TL;DR

This paper introduces a spatial cross spectrum technique to reduce incoherent convective background noise in helioseismic measurements, enhancing the detection of low-frequency solar oscillation modes.

Contribution

It presents a novel application of spatial cross spectrum analysis to improve helioseismic signal detection by leveraging differences in spatial scales of solar motions.

Findings

Effective reduction of convective background noise in helioseismic data.

Enhanced signal-to-noise ratio for low-frequency solar oscillations.

Validation using VIRGO/LOI and GONG data sets.

Abstract

Measurements of low-order p modes and gravity modes are perturbed by the solar convective background. Such perturbation increases below 2mHz for intensity measurements and 1mHz for velocity measurements. While the low-degree modes have large spatial scales, the convective motions have much smaller spatial distribution. In this work, we take advantage of these different scale sizes to explore the use of spatial cross spectrum between different regions of the Sun. The aim is to reduce the incoherent background noise and, therefore, increase the signal-to-noise ratio of the signals that are coherent across the full disk. To do so we use the VIRGO/LOI instrument aboard SoHO and the GONG ground-based network to study the intensity and velocity spatial cross spectra.