Universal Plasma Boundary at χ = 0.15: An Empirical Discovery from Multi-Environment Observations

We report the empirical discovery of a universal boundary in plasma perturbations across multiple space environments. Analysis of 1,480,000+ observations from DSCOVR (Earth solar wind, 2016–2026), MAVEN (Mars magnetotail, 2019–2025), and USGS ground magnetometers (2025) reveals that normalized perturbations never exceed χ = 0.15, where χ ≡ max(|δB/B|, |δn/n|, |δV/V|). Zero violations were observed across all datasets. Approximately 52% of observations cluster near the boundary (0.145 ≤ χ ≤ 0.155), suggesting an attractor state. The boundary matches the electron-to-proton mass ratio: χ ≈ (m_e/m_p)^(1/4) ≈ 0.153 (1.3% precision). This work provides testable predictions for reconnection sites, CME shocks, and plasma boundaries observable by current missions (MMS, Solar Orbiter, Parker Solar Probe, Plasma Observatory).