On the solar origin of the 220.7 signal

TL;DR

This paper investigates a persistent 220.7 muHz signal in helioseismic data, providing evidence that it originates from the Sun rather than instrumental effects, and discusses its potential link to solar g modes.

Contribution

The study confirms the solar origin of the 220.7 muHz signal and rules out instrumental artifacts, supporting its association with solar g modes.

Findings

The 220.7 muHz signal is present across multiple helioseismic instruments.

Instrumental effects are unlikely to produce the 220.7 muHz signal.

The signal is consistent with a solar g-mode origin.

Abstract

Gravity modes in the Sun have been long searched during the past decades. Using their asymptotic properties Garcia et al. (2007) found the signature of the dipole g modes analyzing an spectral window between 25 and 140 muHz of velocity power spectrum obtained from the GOLF/SoHO instrument. Using this result it has been possible to check some properties of the structure of the solar interior (Garcia, Mathur & Ballot 2008) as well as some indications on the dynamics of the core. However, the individual detection of such modes remains evasive and they are needed to really improve our knowledge of the deepest layers in the Sun (Mathur et al. 2008). In this work we study the signal at 220.7 muHz which is present in most of the helioseismic instruments during the last 10 years. This signal has been previously identified as part of a g-mode candidate in the GOLF data (Turck-Chieze et al. 2004; Mathur et al. 2007) and in SPM/VIRGO (Garcia et al. 2008) with more than 90% confidence level. It could be labelled as the l=2 n=-3 g mode as it is in the region were this mode is expected. We have checked the possibility that the 220.7 muHz signal could have an instrumental origin without success by analysing all the available housekeeping data as well as the information on the roll, pith and yaw of the SoHO spacecraft. In consequence, we are confident that this signal has a solar origin.