Stable Solar Periodicities: The Time Stability

TL;DR

This paper introduces a novel measure of time stability based on coherence to identify persistent solar periodicities, providing insights into the connection between interior and exterior solar activities.

Contribution

It proposes a stability-based significance criterion for spectral analysis, emphasizing coherence over amplitude, to detect time-stable solar periodicities.

Findings

Most periodicities in exterior solar activity originate from interior activity.

Time stability effectively identifies persistent solar cycles.

Coherence-based analysis reveals connections between different solar phenomena.

Abstract

We show that while the Fourier transform can figure only an "intensity" of a periodic signal, there is an additional information embedded, which is a "coherence" of the signal. Supposing that the periodicity is reflected only on the "coherence," we introduce a time stability as a measure of "coherence" excluding the "intensity," i.e. amplitude of signal. In stead of classical strength-based significance, where strength implies the power or amplitude, we adopt a stability-based significance as criterion to choose cycles in a random signal. We inspect the time-stable solar periodicities and show that most periodicities discovered in exterior solar activities such as the solar wind inhere in interior solar activity such as the sunspot and that the time stability can be an effective tool in spectral analysis of stochastic solar activity.