Are short-term variations in solar oscillation frequencies the signature of a second solar dynamo?

TL;DR

This paper investigates short-term 2-year variations in solar oscillation frequencies, suggesting they may originate from a second solar dynamo separate from the main 11-year cycle, based on multi-instrument observations.

Contribution

It provides evidence of a quasi-biennial signal in solar oscillations and explores its potential origin as a second dynamo near the solar surface.

Findings

Detected a 2-year signal in solar p-mode frequencies across multiple datasets.

The 2-year signal is influenced by but distinct from the 11-year cycle.

Proposed the existence of a second dynamo near the solar surface.

Abstract

In addition to the well-known 11-year solar cycle, the Sun's magnetic activity also shows significant variation on shorter time scales, e.g. between one and two years. We observe a quasi-biennial (2-year) signal in the solar p-mode oscillation frequencies, which are sensitive probes of the solar interior. The signal is visible in Sun-as-a-star data observed by different instruments and here we describe the results obtained using BiSON, GOLF, and VIRGO data. Our results imply that the 2-year signal is susceptible to the influence of the main 11-year solar cycle. However, the source of the signal appears to be separate from that of the 11-year cycle. We speculate as to whether it might be the signature of a second dynamo, located in the region of near-surface rotational shear.