The Sun's Magnetic Power Spectra Over Two Solar Cycles. I. Calibration Between SDO/HMI And SOHO/MDI Magnetograms

• DOI: 10.48550/arxiv.2308.07530
• Publication Date: 2023-01-01
• Authors: Yükun Luo; Jie Jiang; Ruihui Wang
• Keywords: Maxima and minima

The Sun's magnetic field is strongly structured over a broad range of scales. spatial power spectral analysis provides powerful tool to understand the various scales fields and their interaction with plasma motion. We aim investigate spectra using spherical harmonic decomposition high-resolution SOHO/MDI SDO/HMI synoptic magnetograms covering three consecutive solar cycle minima in series papers. As first series, we calibrate analyze based on co-temporal data this paper. For time, find that calibration factor $r$ between varies scale $l$ field, where degree harmonics. satisfies $r(l)=\sqrt{-0.021 l^{0.64}+2} \quad(5<\mathrm{l}\leq539)$. With function, most contemporaneous show consistent from about 8 Mm global 3 orders magnitudes. Moreover, maps peaks/knees at $l\approx120$ corresponding typical supergranular (about 35 Mm) constrained direct velocimetric measurements. This study paves way for investigating solar-cycle dependence supergranulation subsequent studies.