Unexplained Bright–Dim Intensity Asymmetries in SOHO/UVCS Lyman-α Data

Abstract (Observational Astrophysics; Preprint)

We present a permutation test analysis of 334 daily sequences of SOHO/UVCS Lyman-α spectra (2007–2009). By splitting frames into bright and dim subsets and comparing their median intensity and wavelength, we test whether observed differences exceed those expected from random sampling. We find that 163 of 321 day–radial bins (51%) exhibit statistically significant bright–dim intensity contrasts at false discovery rate (FDR) 5%. The effect is modest (Cohen’s d ≈ 0.24) but robust to permutation. Velocity differences are not significant (d ≈ −0.03). The origin of this asymmetry is unknown: it may reflect solar structures, instrumental systematics, or unexplored physical processes. We publish these results as an open anomaly to encourage community investigation.